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Bureau of Mines Information Circular/1985 




Control of Acid Mine Drainage 

Proceedings of a Technology Transfer 
Seminar 



By Staff, Bureau of Mines 



If- 



5bv.>c 



UNITED STATES DEPARTMENT OF THE INTERIOR 



C 

x 
m 

> 
c 

9c 



j^S^^^ I 



^(NES 75TH AV'*'^ 






Information Circular 9027 



Control of Acid Mine Drainage 

Proceedings of a Technology Transfer 
Seminar 



By Staff, Bureau of Mines 




UNITED STATES DEPARTMENT OF THE INTERIOR 

Donald Paul Hodel, Secretary 

BUREAU OF MINES 
Robert C. Norton, Director 



1 






1 



CONTENTS 



Abstract 

Introduction , 

Prediction of Acid Drainage Potential in Advance of Mining, by Patricia M. 

Erickson, Richard W. Hammack, and Robert L, P. Kleinmann , 

Hydrologic Aspects of Acid Mine Drainage Control, by Kenneth J. Ladwig , 

Oxygen Content of Unsaturated Coal Mine Waste, by Patricia M. Erickson , 

Control of Acid Mine Drainage by Application of Bactericidal Materials, by 

Patricia M. Erickson, Robert L. P. Kleinmann, and Steven J. Onysko , 

Alkaline Injection: An Overview of Recent Work, by Kenneth J. Ladwig, 

Patricia M. Erickson, and Robert L. P. Kleinmann , 

Comparative Tests To Remove I-langanese From Acid Mine Drainage, by George R. 

Watzlaf , 

Treatment of Acid Mine Water by Wetlands, by Robert L. P. Kleinmann , 

In-Line Aeration and Treatment of Acid Mine Drainage: Performance and Prelimi- 
nary Design Criteria, by Terry Ackman and Robert L. P. Kleinmann 



Page 



1 


2 


3 


12 


19 


25 


35 


41 


48 


53 



UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 

With Factors for Conversion to U.S. Customary Units 
and the International System of Units (SI) ' 



Abbreviation 


Unit of measure 


To convert to — 


Multiply by- 


- 


or unit 










acre 


acre 


hectares 


0.405 




cm 


centimeter 


inches 


0.3937 




ft 


foot 


meters 


0.3048 




ft2 


square foot 


square centimeter 


929.0 




ft3 


cubic foot 


cubic meters 


0.028 




ft/s 


foot per second 


centimeters per second 


30.48 




g 


gram 


ounces 


0.0353 




gal 


gallon 


liters 


3.785 




gal/h 


gallon per hour 


liters per hour 


3.785 




gal/min 


gallon per minute 


liters per minute 


3.785 




h 


hour 


NAp 






ha 


hectare 


acres 


2.471 




in 


inch 


centimeters 


2.54 




kg 


kilogram 


pounds 


2.205 




L 


liter 


cubic inches 


61.025 




lb 


pound 


kilograms 


0.4536 




Ib/min 


pound per minute 


kilograms per minute 


0.4536 




L/min 


liter per minute 


gallons per minute 


0.2642 




m 


meter 


feet 


3.28 




m3 


cubic meter 


cubic yards 


1.308 




mVs 


cubic meter per second 


gallons per second 


264.2 




mile 


mile 


kilometers 


1.609 




mg 


milligram 


grains 


0.0154 




mg/L 


milligram per liter 


NAp 






mg/(L-h) 


milligram per liter per hour 


NAp 






min 


minute 


NAp 






mL 


milliliter 


cubic inches 


0.061 




mm 


millimeter 


inches 


0.0394 




mmho/m 


millimho per meter 


NAp 






ym 


micrometer 


inches 


3.94 X 10- 


5 


pet 


percent 


NAp 






psi 


pound per square inch 


grams per square 
centimeter 


70.307 




std ft^/min 


standard cubic foot per 
minute 


NAp 






ton 


ton 


metric tons 


0.907 




yr 


year 


NAp 







NAp Not applicable. 

^ Owing to the preference of individual authors, U.S. customary and 
both been used in this report. Conversion factors are provided for the 
the reader. 



SI units have 
assistance of 



CONTROL OF ACID MINE DRAINAGE 

Proceedings of o Technology Transfer Seminar 

By Staff, Bureau of Mines 



ABSTRACT 

Acid mine drainage can be controlled by water treatment, retardation 
of the pyrite oxidation reaction system, or enhanced prediction that 
allows preventive action to be taken. The Bureau of Mines is conduct- 
ing research in each of these areas; the results of this research are 
summarized in the eight papers that comprise this volume. Field work, 
to evaluate overburden analysis, alkaline injection, and bactericidal 
control of acid formation is described, along with two new inexpensive 
methods to treat acid mine water. These papers were prepared for an 
acid mine drainage technology transfer meeting held in Pittsburgh, PA, 
on April 3 and 4, 1985. 



INTRODUCTION 



Acid drainage from coal mines is one 
of the most persistent industrial pollu- 
tion problems in the United States. Over 
5,000 miles of streams and rivers are 
adversely affected, primarily by under- 
ground mines that have been abandoned 
for decades. Meanwhile, at active mining 
operations and at sites where mining oc- 
curred after 1977, discharge water must 
be treated to meet fairly stringent regu- 
latory limits — at a cost to the industry 
of over $1 million per day. 

The Bureau of Mines has a special re- 
sponsibility to facilitate integration of 
mining and mineral processing with envi- 
ronmental safeguards. This responsibil- 
ity is twofold: the development of tech- 
niques to reduce or eliminate environmen- 
tal degradation, and the Improvement of 
existing pollution control processes to 
make them more efficient and more cost 
effective. Research in acid mine drain- 
age exemplifies the Bureau's concern for 
these environmental aspects of mining. 

This collection of papers summarizes 
much of the Bureau's recent research on 
acid mine drainage and will give the 
reader a sense of where the research is 
headed, in addition to providing details 
regarding new technology and recently ac- 
quired knowledge. The research papers 
address four basic objectives: 

1. Improved prediction of acid poten- 
tial. — The Bureau is attempting to ad- 
dress three fundamental problems associ- 
ated with premine prediction of acid mine 
water: (1) the lack of field verifica- 
tion for currently available techniques 
using overburden analysis, (2) difficul- 
ties encountered when one attempts to in- 
corporate pyrite reactivity and kinetics 
into premine prediction, and (3) incor- 
porating the effectiveness of reclamation 
measures in predicting eventual acid pro- 
duction. Available techniques are being 
evaluated at sites where the extent of 
acid production from reclaimed spoil can 
be monitored. This will enable the Bu- 
reau to evaluate their applicability and 



the effect of potentially mltigrating 
measures taken by the mining companies. 
This research should lead to better per- 
mitting by State agencies, improved mine 
planning, and improved reclamation. 

2. Improved mine planning. — Improved 
prediction will allow an awareness of the 
potential problem, but the effect that 
mining methods and procedural changes 
will have on the extent of the problem 
must still be systematically determined. 
Fundamental aspects of such factors as 
hydrology and oxygen diffusion must be 
understood before modified reclamation 
plans and new closure methodology can be 
developed to prevent acid mine drainage 
in the future. 

3. At-source control of acid forma- 
tion. — Current Bureau research indicates 
that it is possible to reduce acid loads 
under certain conditions using long-term 
inhibition of bacterial catalysis at or 
near the surface, or chemical treatment 
to reduce pyrite reactivity. The lat- 
ter will most likely require the estab- 
lishment of a near-neutral pH regime or 
low-Eh environment. Reduced acid loads, 
although less desirable than total 
prevention, are now achievable. Water 
treatment costs and reclamation costs can 
both be reduced if acid production is 
decreased. 

4. Improved water treatment. — The Bu- 
reau has developed two low-cost alterna- 
tives to conventional mine water treat- 
ment facilities. For low flows of acid 
water, a low-maintenance system, consist- 
ing of a Sphagnum moss wetland to remove 
iron, followed by limestone neutraliza- 
tion, has been demonstrated to be effec- 
tive in a pilot-scale test; full-scale 
tests are in progress. For higher flows, 
the Bureau has developed a pipeline neu- 
tralization and aeration system that can 
be scaled up or down to meet most treat- 
ment needs; the entire system costs only 
a few thousand dollars and appears to be 
more efficient than a conventional treat- 
ment facility. 



PREDICTION OF ACID DRAINAGE POTENTIAL IN ADVANCE OF MINING 

By Patricia M. Erickson,^ Richard W. Haramack.,2 
and Robert L. P. Kleinmann^ 



INTRODUCTION 



Surface coal mine operators are re- 
quired by law to identify the potential 
for acidic drainage prior to opening a 
new mine (9^).'^ In many cases, particu- 
larly in the Appalachian region, the per- 
mit application must contain the results 
of overburden analyses intended to quan- 
tify the acidic or alkaline weathering 
products of the affected strata. These 
data serve two purposes: to provide the 
regulatory agency with a means to esti- 
mate the hydrologic consequences of the 
proposed mine, and to allow the proposed 
operator to plan the mine with regard for 
probable water treatment requirements. 
Until the Bureau's current project, there 
has been no systematic field evaluation 
of these analytical techniques. 

The acid-base account is the most com- 
monly used overburden analysis technique 
(6) . The method is based on measuring 
the total sulfur content of each litho- 
logic unit and converting that value to 
an acid potential based on the stoichio- 
metry of complete pyrite oxidation. Sim- 
ilarly, the neutralization potential is 
determined for each lithology by its 
ability to neutralize strong acid. The 
two values, acid and alkaline potential, 
respectively, are represented as calcium 
carbonate equivalents for calculation of 
a net excess or deficiency of neutral- 
izers. A deficiency greater than 5 tons 
CaC03 per 1,000 tons of rock is generally 
considered a potential source of acid 
mine drainage (11). 

^Supervisory physical scientist. 

^Geologist. 

■^Researcn supervisor. 
Pittsburgh Research Center, Bureau of 
Mines, Pittsburgh, PA. 

'^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this paper. 



The acid-base account uses rapid and 
simple analytical techniques; it is, 
therefore, inexpensive. The results, 
however, indicate only the total acid and 
alkaline loads that could be produced if 
all the pyrite and carbonates reacted. 
The major flaw in interpreting these data 
for water quality is that reaction kinet- 
ics are ignored. Complete oxidation of 
pyrite may take decades, even if all the 
pyrite is reactive; acidity in solution 
is determined by the rate of oxidation 
and flushing. 

In contrast, calcium carbonate dis- 
solves rapidly to an equilibrium value of 
approximately 60 mg/L alkalinity at at- 
mospheric CO2 partial pressure (_5) . More 
carbonate mineral dissolves to achieve 
the same equilibrium concentration if 
acidity is present; higher concentrations 
can be dissolved at high carbon dioxide 
partial pressures (]_) • Because solution 
acidity and alkalinity are controlled 
largely by the kinetics and thermodynam- 
ics of many reactions, use of total mass 
balance data to predict water quality is 
suspect. The developers of the acid-base 
account technique did not intend it to 
predict drainage quality, but rather to 
identify strata that may produce acid. 

Other overburden analytical mathods can 
be classified as simulated weathering 
techniques. These have in common that 
the strata, either individually or as a 
thickness-weighted composite, are sub- 
jected to oxidizing conditions to accel- 
erate chemical weathering of the materi- 
als. Chemical composition of drainage 
obtained from periodically leaching the 
sample is classified as acidic or alka- 
line and is presumed to qualitatively 
predict the nature of postmining drainage 
at the proposed mine. 



Oxidative processes can be accelerated 
by heat, addition of chemical oxidants, 
reduced particle size of the solid phase, 
inoculation with bacteria, and other 
means ; innumerable protocols could be de- 
vised for weathering tests. Two methods 
that have been used for overburden anal- 
ysis utilize crushed core samples sub- 
jected to humidified air streams; the 
techniques differ in that one utilizes 
individual weathering tests for each 
lithology (2) and the other utilizes a 
composite sample assembled according to 
the backfilling plan (8^) . 

Weathering tests may provide a real- 
istic estimate of postmining drainage 
quality if they duplicate the kinetics 
of relevant reactions under field condi- 
tions. These tests require longer pe- 
riods of time, from several weeks to 
months, and are more expensive to use 
than the acid-base account technique. 
The accuracy of any simulated weathering 
technique must be verified to determine 
its predictive capability. 

Prediction of acid drainage potential 
from overburden analyses and other pre- 
mining data relies on interpretation by 



mine operators , consultants , and regu- 
latory personnel. The data merely indi- 
cate the maximum acid and alkaline loads 
(acid-base account) or drainage quality 
under a given set of conditions (weather- 
ing tests). Effects of mining-related 
factors such as mining method, use of se- 
lective handling, and ameliorant applica- 
tions are not considered in overburden 
analysis. There is no consensus on a 
method to combine the lithologic data, 
mining plans, and reclamation plans into 
a predictive scheme. 

The Bureau is currently conducting 
contract and in-house research to im- 
prove acid drainage prediction. The con- 
tract research consists of two phases: 
(1) field evaluation of three overburden 
analytical techniques at 30 mine sites 
and (2) design of an empirical predictive 
scheme that encompasses overburden data 
and site-specific factors that could in- 
fluence actual drainage quality. The 
in-house research is oriented toward de- 
veloping an alternative overburden analy- 
sis method that takes into account pyrite 
reactivity. Both projects are discussed 
in following sections. 



CONTRACT RESEARCH PROGRAM—PREMINING PREDICTION OF ACID DRAINAGE POTENTIAL 



The Bureau awarded a research contract 
to Engineers International, Inc., in 1982 
to improve the state of premining pre- 
diction. Phase 1, nearly complete now, 
addresses the validity of using available 
overburden analysis techniques to predict 
postmining drainage quality. Phase 2 
will focus on the development of an em- 
pirical predictive scheme encompassing 
mining-related variables. 

FIELD EVALUATION OF OVERBURDEN ANALYSIS 

The objective of this phase of the re- 
search is to determine the utility of 
three overburden analysis techniques for 
predicting drainage quality after mining. 
To accomplish this goal within a reason- 
able time, the program plan called for 
the collection of actual postmining data 



and the equivalent of premining overbur- 
den data from 30 reclaimed mines. The 
validity of this phase depends mainly on 
obtaining overburden samples that rep- 
resent the overburden in the reclaimed 
section. At nine sites, cores sampled 
less than 1 yr ago were available for 
analysis. At the remaining sites, chan- 
nel samples from an active highwall adja- 
cent to each reclaimed mine section (used 
as the postmining water data source) were 
collected for overburden analysis. This 
method was chosen for two reasons: 
(1) The cost was much lower than the cost 
of drilling cores on adjacent unmined 
land, and (2) visual observation could be 
checked against company records to verify 
continuity of the overburden lithology. 
Fresh material was exposed on the high- 
wall before sampling. 



Site-selection criteria were designed 
to ensure that the predictive capabili- 
ties of the overburden analysis methods 
would be evaluated. Historical records, 
provided by State regulatory agencies and 
the coal companies , were used to elimi- 
nate mine sites having significant net 
acid or alkaline potential. It was felt 
that any overburden analysis technique 
can adequately predict an acid or alka- 
line discharge when the carbonate or py- 
rite is totally absent, respectively; the 
target sites were those that are present- 
ly difficult to assess. 

In some cases, disagreement between 
overburden analysis results at the time 
of permitting and actual drainage qual- 
ity was used to select a site; in other 
cases, professional judgment had to be 
used. Sites at which nonstandard prac- 
tices might be the significant determi- 
nant in postmining drainage quality were 
avoided. These included backfills con- 
taining acid drainage treatment sludge, 
fly ash or preparation plant refuse, and 
sites treated with ameliorative chemicals 
other than agricultural limestone and 
fertilizer. 

Samples were subjected to laboratory 
analyses. Acid-base accounting was used 
on the samples from all 30 sites; weath- 
ering tests published by Caruccio (2^) and 
Sturey (8^) were performed on samples from 
16 and 5 sites, respectively. Cold alka- 
linity determinations were also made on 
Caruccio weathering test samples. Table 
1 illustrates other types of information 
obtained from adjacent areas and avail- 
able records added to the premining data 
set. 

The most critical postmining data in- 
volved the quality of water issuing from 
the reclaimed mine section. To charac- 
terize the drainage, a field monitoring 
program was instituted at each site to 
measure the volume and quality of dis- 
charges at least eight times during a 
1-yr period. Analyses are indicated in 
table 2. Where possible, data collected 
by the mine operator were also used. 



TABLE 1, - Premining equivalent data 
collected to supplement overburden 
sampling and analysis 



Information 

Local geology, 
hydrology , 
and mining 
history. 

Surface and 
ground water 
quality and 
quantity. 

Climatic data. 



Sources 

Permit applications. 
State and Federal 
agencies . 

Current project, 
historical records. 



Government records, 
mining company records, 



TABLE 2. - Analyses performed on 
premining and postmining water 
samples 



Field measurements Laboratory analyses 



SUITE 1 



pH... 
Acidi 
Disso 
Speci 
Tempe 



ty, alkalinity. 
Ived oxygen. . . . 
fie conductance 
rature 



Iron 
Sulfate 



SUITE 2 




pH 




Iron 


Acidity, alkalinity. 




Sulfate 


Dissolved oxygen.... 




Calcium 


Specific conductance 




Magnesium 


Temperature 




Manganese 





SUITE 3 




pH 




Iron 


Acidity, alkalinity. 




Sulfate 


Dissolved oxygen.... 




Calcium 


Specific conductance 




Magnesium 


Temperature. ........ 




Manganese 
Aluminum 







Table 3 summarizes ancillary postmining 
data, collected primarily for use in 
phase 2. 

Phase 1 data collection is now com- 
plete, and statistical analysis is in 
progress. Table 4 summarizes the ranges 
of values for acid-base account parame- 
ters observed in samples from 30 sites. 
The most acidic thickness-weighted value 
for a single overburden column was a 



TABLE 3. - Supplementary postmining data 



Mining Maps. 

Drilling logs. 

Mining method and equipment. 

Materials handling. 

Reclamation Backfilling plans and maps. 
Materials handling. 
Equipment. 

Chronological records. 
Topsoil storage. 
Soil amendments. 
Vegetation. 

TABLE 4. - Ranges of values of acid-base 
account parameters for individual 
lithologies 



TABLE 5. - Average leachate quality 
range for Caruccio weathering 
tests on individual lithologies 



Parameter 



Range 



pH, paste.... 3.0- 7.9 

Sulfur, pet: 

Total <.05- 8.3 

Pyritic <.05- 7.2 

Sulfate <.05- .73 

Organic <.05- .31 

Neutralization potential 

per 1,000 tons CaC03 -2.7 -940 

deficiency of 1,300 tons as calcium car- 
bonate. At the other extreme was a West 
Virginia site having an excess alkalinity 
of 1,200 tons as calcium carbonate. In- 
terestingly, one of several toe-of -spoil 
seeps at the latter site is acidic. 

The Caruccio weathering test was per- 
formed on overburden samples from 16 
sites, having acid-base account results 
Indicating overall neutrality (6 sites), 
acidity (5 sites), or alkalinity (5 
sites). Ranges of cumulative leachate 
quality for individual lithologies are 
shown in table 5. 

The quality of surface runoff and spoil 
seepage are the dependent variables for 
statistical analysis in phase 1. Three 
sets of primary independent variables 
were derived from the three overburden 
analysis methods used in the study. An- 
cillary data (tables 1 and 3) will be 
used in this analysis only as needed to 



Parameter 

Acidity, as CaC03 : 

Hot total 

Mineral 

Alkalinity 

Sulfate 



Concentration 
range, mg/L 



<l-53,000 

0-13,000 

<1- 380 

<l-33,000 



classify sites in the case of bimodal 
distributions. For example, sites may be 
classified by degree of vegetative cover, 
time since mining, or other factors. 
Significant correlations between depen- 
dent and independent variables will be 
identified by simple linear regression 
analysis, factor analysis, and multivari- 
ate regression analysis. The phase 1 re- 
search product will be a set of equations 
that relate observed drainage quality to 
overburden analysis data. 

EMPIRICAL PREDICTIVE METHOD 

Phase 2 of the contract research 
will focus on the design and testing of a 
method to predict postmining drainage 
quality. This phase of the research will 
make extensive use of the data developed 
during phase 1. Our working hypothesis 
is that the mining-related factors play 
a critical role in the observed drainage 
quality. Therefore, we expect that the 
phase 1 results will indicate moderate 
correlation coefficients between overbur- 
den analysis data and postmining drainage 
quality. The objective of phase 2, then, 
is to improve the prediction by including 
the nonnumerical (categorical) factors 
shown in tables 1 and 3. 

The output of the research may come in 
different forms. For example, there may 
be a nonlinear equation in which non- 
numeric factors have been assigned nu- 
merical rankings. Alternatively, the 
predictive method may be based on an n- 
dimensional decision surface, as in pat- 
tern recognition. 



IN-HOUSE RESEARCH: PYRITE REACTIVITY ANALYSIS 



BACKGROUND 

Acid-base accounting methods depend 
upon sulfur analysis to accurately quan- 
tify the potential acidity of overburden 
materials. Potential acidity is general- 
ly considered to be a function of the 
total sulfur content, although only py- 
ritic sulfur contributes significantly 
to acid production. Pyritic sulfur must 
be distinguished from non-acid-producing 
sulfur forms, in cases where (1) the ma- 
terial is weathered and much of the orig- 
inal pyritic sulfur has been oxidized to 
sulfate sulfur or (2) the material is 
carbonaceous and a significant proportion 
of the total sulfur is bonded to organic 
molecules . 

Pyrite occurs as different forms or 
morphologies in coal and overburden mate- 
rials. Many authors have provided petro- 
graphic descriptions of various pyrite 
morphologies; descriptions given by King 
(_3) have been adopted for this study be- 
cause they are usable and encompass all 
pyrite morphologies. According to King, 
pyrite occurs in five basic morphologies: 
(1) spherical aggregates of euhedral py- 
rite crystals (framboids), (2) isolated 
euhedral pyrite crystals, (3) nonspheri- 
cal aggregates of euhedral pyrite crys- 
tals, (4) irregularly shaped massive py- 
rite, and (5) fracture-filling massive 
pyrite. 

Differences in pyrite reactivity corre- 
lative to different pyrite morphologies 
were first noted by Caruccio (J^) . Caruc- 
cio indicated that framboidal pyrite was 
the most reactive pyrite form and related 
the percentage of framboidal pyrite to 
the acid-producing potential of selected 
samples. Most researchers agree that, in 
general, the smaller the grain of pyrite, 
the more reactive the pyrite and the 
greater the potential acidity. 

The importance of reactive pyrite forms 
in the generation of acid mine drainage 
was generally dismissed when it was real- 
ized that these fonns could not account 



for all of the acidity observed. Howev- 
er, the oxidation of reactive forms under 
ambient conditions may establish a chem- 
ical environment that favors bacterial 
catalysis and permits the less reactive 
pyrite to react. Research into this pos- 
sible triggering mechanism may identify 
parameters that are inherently more accu- 
rate in predicting potential acidity than 
total sulfur or pyritic sulfur content 
alone. Quantification of reactive pyrite 
forms would not be able to predict total 
acidity but would allow for more accurate 
assessment of pyrite oxidation rates, and 
thus possibly distinguish "go" or "no go" 
acid generation situations. Initial Bu- 
reau research into pyrite reactivity was 
based on the hypothesis that different 
pyrite morphologies and grain sizes would 
thermally decompose and oxidize at dif- 
ferent temperatures corresponding to the 
relative stability of each form; more re- 
active forms would be expected to react 
at lower temperatures because of lower 
activation energies. 

Previous studies have used thermogravi- 
metric (TG) and differential thermal 
analysis techniques (DTA) to investigate 
the thermal behavior of museum-grade py- 
rite and marcasite. Warne (10) used DTA 
thermograms to identify pyrite and mar- 
casite in coal, carbonate, and clay ma- 
trices. He found that minimum pyrite 
concentrations of 0.5 to 1.0 pet could be 
detected in a coal matrix by DTA despite 
kaolinite and ankerite interferences. 
However, DTA thermograms of pyrite and 
marcasite were so similar that they could 
not be differentiated. Luganov (4^) ob- 
served the thermal behavior of pyrite 
under inert atmospheres. They found that 
DTA's of pyrite displayed an exothermic 
effect at 380° C followed by endother- 
mic effects at 480° to 500° C, 550° to 
570° C. The exothermic effect at 380° C 
was attributed to partial oxidation of 
pyrite by oxygen adsorbed on the surface. 
Subsequent endothermic effects at 480° 
to 500° C and 550° to 570° C were thought 
to represent the reaction of exothermic 
products with pyrite. DTA's of pyrite 



treated with acid and ethanol to dissolve 
ferric oxides and remove adsorbed oxygen 
displayed only an endothermic effect at 
680° C. 

EXPERIMENTAL WORK 

A modified evolved-gas analysis tech- 
nique was used to examine the thermal be- 
havior of sulfur species. This technique 
employs a resistance furnace for the pro- 
grammed heating of coal and overburden 
samples in an oxygen atmosphere. The 
evolution of sulfur dioxide and sulfur 
trioxide gases was measured by an infra- 
red detector and recorded simultaneously 
with the sample temperature on a two- 
channel recorder. A Leco SC-32 Sulfur 
Analyzer^ was used to ignite samples and 
monitor the evolution of sulfur oxides. 

Initial tests of the evolved-gas analy- 
sis technique were made to determine if 
pyritic and sulfate sulfur could be 
thermally distinguished. Figure 1 is a 
thermogram of a sample containing 0.480 g 
Fe2(S04)3*H20 and 0.020 g FeS2 (pyrite). 
Results of this test indicate that pyrit- 
ic sulfur and sulfate sulfur can be tem- 
porally differentiated or time-resolved 
at an isothermal furnace temperature of 
767° C. Hydrated sulfate salts of cal- 
cium, magnesium, manganese, and ferrous 



iron were also tested; the sulfate inter- 
ference in all cases constituted less 
than 1 pet of the total pyrite response. 

Standards of museum-grade pyrite were 
prepared in a silica gel matrix and 
tested at a furnace temperature of 
767° C. Time-resolved, evolved-gas ther- 
mograms of pyrite standards are shown in 
figure 2. A plot of peak area for char- 
acteristic pyrite peaks versus the con- 
centration of pyrite standards (fig. 3) 
yields a linear relationship. This indi- 
cates that the Leco SC-32 Sulfur Analyzer 
may be useful for quantification of py- 
ritic and sulfate sulfur species in sam- 
ples of low carbon content. The effect 
of carbonaceous material on pyrite ther- 
mograms is shown in figure 4. The large 
exothermic effect resulting from the com- 
bustion of carbonaceous materials effec- 
tively masks all pyrite peaks. Interac- 
tion of pyrite with the organic matrix 
and pyrolysis products may result in the 
shifting of characteristic pyrite peaks. 

The relative reactivity of framboidal 
and isolated euhedral pyrite morpholo- 
gies was compared by preparing a 3-pct-S 

^Reference to specific products does 
not imply endorsement by the Bureau of 
Mines . 



UJ 

o 

z 
< 

CD 

o 

CO 
CD 

< 

UJ 

> 

_l 

LJ 



T 



_Pyrite_ 
response 



H h 







"1 1 

Furnace temp- 767 **C 



Sulfate response 





4 6 

TIME, min 

FIGURE 1. - Time-resolved, evolved-gas analysis of a sample containing 0.20 g pyrite and 0.480 g 
Fe2(S04)3.H20. 



1.0 



LU 
O 

< 
CD 

cr 
o 

CO 
CD 

< 

LU 

> 

< 

-I 
LU 



.5 - 



' KEY ' 
0.75 pet sulfur (pyrite) 
0.50 pet sulfur (pyrite) 
0.25 pet sulfur (pyrite) 
Furnace temp= 767° C 




I 2 

TIME, min 

FIGURE 2. - Time-resolved, evolved-gas analy- 
sis of pyrite standords. 



o 

CL 



LlI 

cr 

>■ 

Q. 

CO 
< 

a: 



Z) 
CO 




2 3 

PEAK AREA 

FIGURE 3. - Plot of cumulative pyrite peck 
area versus sulfur content. 









1 1 1 1 I > 




800 






3 








700 




liJ 






/ \^ 









13 






/ N. 








Z 






/ N. 




600 


III 


< 






/ \^ 






rr 


m 






/ ^N. 






— ) 


o 

CO 


;d 




/ t<EY ^-- 




500 




III 




III 


< 




_ 


i'', / Absorbance 




400 


a. 


LiJ 






I 1 / r^^ Furnace temp^ 400° C 






hi 


> 






\r ~"-. 




300 


H 


_i 
u 
q: 


1 


\^ 


1 -■--, 




200 


UJ 
_l 
CL 

< 






/ 


1 '^^^ 

1 

I 1 1 1 1 Y 




100 


en 






1 













1 2 3 4 5 6 


7" 










TIME, min 









FIGURE 4. - Evolved-gas analysis of carbona- 
ceous sample. 



4.5 
4.0 
3.5 
3.0 
2.5 
2.0 
1.5 



UJ 

o 

z 
< 

CD 
CC 

o 
1) 

CD 
< 

UJ 

> 



UJ 

a: 





1 1 1 1 
KEY 


1 




_ 


— Isolated euhedral pyrife 


1 




— 


— Framboidal pyrife 


: 




— 


— Heating curve 






— 


-- Exothermal effects 








Furnace temp^ 538° C 


£ 






1 


i 
:: 






i! 
j! 
i! 


l^ 


. 


- 


/ i ! 
/ i 1 


> • 


- 




i i 


• 


- 








- 



o 

o 
UJ 

vc 
q: 

UJ 
CL 

s 

UJ 



600 
500 
400 
300 
200 
100 



12 3 4 5 6 7 

TIME, min 

FIGURE 5. - Evolved-gas analysis of isolated 
euhedral and framboidal pyrite morphologies. 

standard of each form in a silica gel ma- 
trix (100- to 200-mesh). Framboidal py- 
rite was supplied by Dr. Alfred Stiller 
of West Virginia University, who con- 
firmed its purity by Mossbauer spectro- 
scopy. Framboidal and isolated euhedral 
pyrite standards were run individually at 
a furnace temperature of 538° C and at 
purge and lance flows of 4 and 1 L/min, 
respectively. The superimposition of the 
two thermograms (fig. 5) illustrates the 



10 



difference in thermal reactivity between 
framboidal pyrite and the more stable 
isolated euhedral pyrite. At this time, 
no thermograms have been run on samples 
containing both framboidal and isolated 
euhedral pyrite. Therefore, the amount 
of interaction between pyrite forms, if 
any, and the characteristics of the re- 
sulting thermogram cannot be predicted. 

Although Bureau of Mines research into 
pyrite reactivity is still in preliminary 
stages, it can be concluded that — 

1. Pyritic and sulfate sulfur in non- 
carbonaceous materials can be differenti- 
ated using a Leco SC-32 Sulfur Analyzer. 

2. Pyritic sulfur can be quantitative- 
ly determined in noncarbonaceous matrices 
using evolved-gas analysis techniques. 

3. Framboidal and isolated euhedral 
pyrite morphologies differ significantly 
in thermal reactivity. 



4. Carbonaceous materials seriously 
interfere with the evaluation of sulfur 
species using evolved-gas analysis. 



Future Bureau of Mines research 
pyrite reactivity will include — 



into 



1. Investigations of the thermal reac- 
tivity of other pyrite morphologies. 

2. The evaluation of evolved-gas anal- 
ysis as a quantitative technique for de- 
termining pyritic and sulfate sulfur in 
noncarbonaceous materials. 

3. The development of a technique for 
performing routine evolved-gas analy- 
sis of sulfur species in carbonaceous 
materials. 

4. Correlation with contract research. 



REFERENCES 



1. Caruccio, F. T. The Quantifica- 
tion of Reactive Pyrite by Grain Size 
Distribution. Paper in Preprints, Third 
Symposium on Coal Mine Drainage Re- 
search, Pittsburgh, PA, 1970, pp. 123- 
131. 

2. Caruccio, F. T. , and G. Geidel. 
Estimating the Minimum Acid Load That Can 
Be Expected From a Coal Strip Mine. Pa- 
per in Proceedings, 1981 Symposium on 
Surface Mining Hydrology, Sedimentology , 
and Reclamation, Lexington, KY, Dec. 7- 
11, 1981, ed. by D. H. Graves. Univ. KY, 
1981, pp. 117-122. 

3. King, H. M. , and J. J. Renton. The 
Mode of Occurrence and Distribution of 
Sulfur in West Virginia Coals. Paper in 
Carboniferous Coal Guidebook, WV Geol. 
and Econ. Surv. Bull., v. 37, 1979, 
pp. 278-301. 

4. Luganov, V. A,, and V. I. Shabalin. 
Behavior of Pyrite During Heating. Can. 
Metall. Q. , v. 21, 1982, pp. 157-162. 



5. Plummer, N. C, , and F. T. MacKen- 
zie. Predicting Mineral Solubility From 
Rate Data. Am. J. Sci., v. 274, 1974, 
pp. 61-83. 

6, Sobek, A. A., W. A. Schuller, J. R. 
Freeman, and R. M. Smith. Field and Lab- 
oratory Methods Applicable to Overburdens 
and Minesoils. EPA 600/2-78-054, 1978, 
203 pp. 



7. Stumm, W. , 
Aquatic Chemistry, 
pp. 249-257. 



and J. J. Morgan. 
Wiley, 2d ed. , 1981, 



8. Sturey, C. S., J. R. Freeman, J. W. 
Sturm, and T. A. Keeney. Overburden 
Analyses by Acid-Base Accounting and Sim- 
ulated Weathering Studies as a Means of 
Determining the Probable Hydrological 
Consequences of Mining and Reclamation. 
Paper in Proceedings, 1982 Symposium on 
Surface Mining, Hydrology, Sedimentology, 
and Reclamation, Lexington, KY, Dec. 6- 
10, 1982, ed. by D. H. Graves. Univ. KY, 
1982, pp. 163-179. 



11 



9. U.S. Code of Federal Regulations. 
Title 30 — Minerals Resources; Chapter 
VII — Office of Surface Mining, Department 
of the Interior; subchapter G — Surface 
Coal Mining and Reclamation Operation 
Permits; July 1, 1984. 

10. Warne, S. S. J. Identification 
and Evaluation of Materials in Coal by 



Differential Thermal Analysis. 
Fuel, May 1965, pp. 207-215. 



J. Inst. 



11. West Virginia Acid Mine Drainage 
Task Force. Suggested Guidelines For 
Method of Operation in Surface Mining of 
Areas With Potentially Acid Producing 
Materials. 1979, 20 pp. 



12 



HYDROLOGIC ASPECTS OF ACID MINE DEIAINAGE CONTROL 
By Kenneth J. Ladwig^ 



INTRODUCTION 



Water is obviously a principal com- 
ponent of the acid mine drainage (AMD) 
problem, functioning as a reactant in py- 
rite oxidation, as a reaction medium, and 
as a transport medium for oxidation prod- 
ucts. The role of water as a transport 
medium is the focus of one segment of the 
Bureau of Mines AMD program. 

Describing the contaminant transport 
process serves two basic purposes. The 
first is to develop site-specific charac- 
terizations of the hydrology, Including 
defining recharge areas and flow paths, 
estimating rates and volumes of mine wa- 
ter flow, delineating lateral variations 
in water quality, and determining contam- 
inant loads at the discharge. The site- 
specific data are critical to the success 
of any abatement procedure, regardless of 
the technical approach chosen. Efficient 
and cost-effective abatement requires 
knowledge of sources of spoil water re- 
charge, zones of acid production, and 
movement of water through the acid-pro- 
producing zones. 

The second purpose is to examine in 
greater detail the interaction between 
acid production and hydrologic transport. 
While field studies are by nature site 
specific, data obtained from several 
mines will be used to develop a more gen- 
eralized conceptual understanding of the 
transport process. The conceptual model 
will then serve as the basis for Improved 
reclamation and abatement technology. Of 
central Importance in this phase of the 
study are (1) the Interaction of the mine 
water with the other components Involved 
in acid generation and (2) the hydrochem- 
ical evolution of the mine water. 

' Hydrologist, Pittsburgh Research Cen- 
ter, Bureau of Mines, Pittsburgh, PA. 



We Investigated the transport process 
at both underground and surface coal 
mines, with most of the underground mine 
work being done in the northern anthra- 
cite field of eastern Pennsylvania. The 
purpose of this work is to describe the 
hydrogeochemical processes occurring in a 
flooded mine complex. The initial phase 
of this work was reported in RI 8837 
(4). 2 

The surface mine work was done prin- 
cipally at reclaimed surface mines in 
Pennsylvania and West Virginia. Why re- 
claimed sites? The fact that many re- 
claimed mines in these States are still 
producing considerable volumes of AMD at- 
tests to the shortfalls of past and cur- 
rent reclamation practices. By monitor- 
ing these sites, we can examine what went 
wrong, determine what steps might be 
taken to deal with the current problem, 
and develop methods for avoiding similar 
problems in the future. 

Described in the following sections are 
results of a case study conducted at a 
reclaimed surface mine in West Virginia 
and a summary of the underground mine 
study in eastern Pennsylvania. The em- 
phasis is on developing a practical moni- 
toring program and then intergrating the 
site hydrology with the AMD abatement 
plan. While it is unlikely that simple 
hydrologic modification alone will elimi- 
nate the problem, a thorough knowledge of 
site-specific hydrology is fundamental to 
the development and execution of a suc- 
cessful abatement plan. 



^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this report. 



13 



SURFACE MINE CASE STUDY 



SITE DESCRIPTION 



METHODS 



A small abandoned mine site in Upshur 
County, WV , was monitored to evaluate the 
use of bactericidal treatment to control 
AMD. The Lower Kittanning seam was mined 
from the U-shaped, 6-ha site in the late 
1970's. Although the site was completely 
revegetated, including the highwall, the 
area was not regraded to approximate 
original contour. Average spoil thick- 
ness was about 7 m. Present topography 
consists of a 12-m slope at the highwall, 
a relatively flat bench over the mined 
area, and a 12-m outslope leading to a 
toe-of-spoil seep (fig. 1). 



The methods used are standard proce- 
dures for surface and ground water moni- 
toring. Relative to perpetual water 
treatment and AMD abatement costs, the 
methods are not expensive, nor are they 
technically complex. As will be illus- 
trated, monitoring can yield valuable in- 
formation on acid production and movement 
at a surface mine site. Some type of 
spoil water monitoring is highly recom- 
mended prior to initiating abatement 
plans. 



Limit of disturbed area 




Seal*, m 



FIGURE 1. - Map of surface mine study site in Upshur County, WV, showing surface features, well 
locations, and results of an electromagnetic induction survey. 



14 



Following initial site reconnaissance 
to locate all seepage points and describe 
surface features , a series of electromag- 
netic induction (EM) surveys were used to 
describe subsurface features. EM can be 
used at surface mines to help determine 
spoil thickness and variations in thick- 
ness across a site, and to locate wet 
zones, mining relicts (highwalls, side- 
walls, unmined blocks), mine floor struc- 
tures, and zones of acid-producing mate- 
rial (3). While they do not eliminate 
the need for monitoring wells, EM surveys 
help identify potential trouble areas. 
Detailed surveying at the Upshur site 
took just under 2 days to complete. 

Monitoring wells were installed to de- 
fine spoil water flow conditions and 
spoil water quality. Spoil borings were 
drilled to the mine underclay, and wells 
were constructed from 2-in polyvinyl 
chloride pipe, slotted along the lower 
10 ft. The borings were backfilled and 
the wells were sampled using standard 
procedures (_5) . 

Spoil samples were collected from sev- 
eral depths during drilling of the moni- 
toring wells. The samples were used to 
characterize the distribution of materi- 
als present on the site and to help re- 
construct the backfilling sequence. All 
samples were visually classified in the 
field. Selected samples were subjected 
to laboratory tests, including leaching 
tests using the method described by Car- 
uccio (2) . 

Seepage discharge was monitored for 
flow rate and water quality. Both sam- 
pling and flow monitoring were done as 
near to the point of seepage as possible 
to minimize mixing with surface runoff. 
As a compromise between cost, accuracy, 
and maintenance requirements , flow gaging 
was done with a simple V-notch weir con- 
structed from plywood and stainless steel 
il) • The weir was inexpensive and 

reliable. 

RESULTS 

The EM surveys revealed an area of high 
apparent conductivity (greater than 14 



mmho/m) on the northwestern part of the 
site (fig. 1). Progressively lower con- 
ductivities were observed in the direc- 
tion of the seep. Although the cause of 
the high conductivity was not immediately 
known, the area enclosed by the 14-mmho/m 
contour on figure 1 was targeted as a 
possible trouble spot. A more detailed 
description of the geophysical survey is 
given elsewhere (_3, site SMI). 

Following the geophysical survey, a 
series of spoil borings were drilled. 
Spoil samples collected during drill- 
ing showed the material in the area of 
high conductivity (wells 4 and 6) con- 
tained significant proportions of a fine- 
grained, black material. In fact, the 
entire thickness of spoil at well site 4 
was comprised of the black material. 
Holes drilled outside the high-conduc- 
tivity zone (wells 1-3, 5, 7-9) contained 
predominantly weathered sandstone. 

The Kittanning coals in the study area 
are "dirty" seams , and the black material 
found at well sites 4 and 6 was believed 
to be coal cleanings or shaly partings. 
Laboratory tests on the spoil material 
showed the mean sulfur content of the 
black material (1.24 pet) was consider- 
ably higher than that of the sandstone 
spoil (0.12 pet). Samples of the under- 
clay were also analyzed and found to have 
a sulfur content similar to that of the 
shaly material (1.20 pet). Of 29 spoil 
samples analyzed, 6 had negative neutral- 
ization potential (4 samples from wells 4 
and 6, and 2 outslope samples). These 
data again point to the area inside the 
14-mmho/m contour in figure 1 as a pri- 
mary trouble spot. 

Final confirmation was provided by mon- 
itor well water samples. The poorest wa- 
ter quality on the site was found in well 
4 (fig. 2). Mean sulfate and acidity 
concentrations at well 4 were about twice 
as high as the average concentrations for 
the spoil and seep. Mean iron concentra- 
tions at well 4 were more than twice the 
mean spoil concentration and more than 
six times the mean seep concentration. 



15 



E 



O 

I- 
< 
CO 



III 

o 

z 

o 
o 



^00 



1.000- 



800- 



600- 



400- 



200- 






• 
• 



9 



O 



9 



Q. 

• 



I 




SULFATE 



ACIDITY 



IRON 



FIGURE 2. - Mean sulfate, acidity, and iron for well 7, well 4, the seep, and averaged for all of the 
wells dri lied into spoi I. 



Conversely, good-quality water was 
found on the southern part of the site, 
particularly near well 7 (fig. 2). The 
well 7 area receives direct inflow of 
highwall seepage, as well as infiltra- 
tion recharge through inert sand soil. 
As a result, there is much less contami- 
nation evident. As this recharge con- 
tinues to migrate through the spoil, the 
water leaches some contaminants and mixes 
with water of poorer quality prior to 
discharge. 

The water quality at the seep lies be- 
tween that found in the well 4 area and 
the well 7 area (fig. 2). Flow at the 



seep is perennial and anomalouly high for 
such a small site. Total seepage dis- 
charge for the 1983 calendar year was 10 
million gal, or about 50 pet of the total 
precipitation for the same period. 

Principally two factors contribute to 
the high volume of discharge. One is the 
uncontrolled highwall seepage into the 
spoil on the southern part of the site. 
The water level in well 7 is the highest 
on the site at all times of the year, in- 
dicating this is a perennial source of 
recharge. The second factor is the ab- 
sence of adequate surface water diver- 
sions on top of the highwall and on the 



16 



loining bench. Surface water from a small 
recharge area above the site flows onto 
the highwall and down a channel on the 
highwall slope. Flows in the channel as 
high as 15 gal/min have been observed 
following a rainstorm. All of the chan- 
nel flow infiltrates directly into the 
spoil before reaching the bottom of the 
slope. The mining bench itself is graded 
back toward the highwall, further stimu- 
lating ponding and infiltration at the 
base of the highwall slope. 

DISCUSSION OF RESULTS 

The hydrologic study at the Upshur site 
suggests at least two avenues for site 
improvement. The first is to attempt to 
abate acid production at the source. The 
primary source of acid production at the 
site appears to be relatively well de- 
fined. Abatement procedures targeted 
directly at the acid-producing area may 
be the most cost-effective means of ob- 
taining a significant reduction in seep 
contamination. 

Application of an organic compound is 
currently being tested at the site to 
inhibit AMD production. The bacteria- 
inhibiting compound, potassium benzoate, 
has been applied at the surface on the 
northeastern part of the site. (The use 
of organic compounds such as benzoate to 
inhibit bacterial catalysis is described 
elsewhere in these proceedings.) The 



effect of the application is being moni- 
tored in lysimeters and wells and at the 
seep. 

The second approach is a simple reduc- 
tion in recharge to the site. For exam- 
ple, subsurface drains to remove clean 
highwall seepage prior to flow through 
the spoil and minimal regarding to pro- 
mote runoff rather than infiltration 
would greatly decrease the total volume 
of water discharged at the seep. Instal- 
lation of these controls would reduce 
mean flow by an estimated 50 to 75 pet 
and very likely change the character of 
the seep from perennial to intermittent. 
Although contaminant concentrations at 
the seep might increase following flow 
reduction measures , we expect the reduced 
volume would more than offset the in- 
creased concentration, resulting in a net 
decrease in contaminant load. 

The case study presented here illus- 
trates the use of relatively inexpensive 
ground water monitoring for targeting AMD 
abatement measures. Data obtained from 
such studies are an integral part of the 
Bureau of Mines research on improving ex- 
isting abatement technology. As an end 
product, this work, in conjunction with 
research on overburden analysis, pyrite 
reactivity, and spoil air, will be used 
to develop predictive methods to avoid 
the pitfalls associated with current min- 
ing and reclamation practice. 



UNDERGROUND MINES 



To study the AMD problem at underground 
mines, the Bureau initiated a field in- 
vestigation of the mine water system in 
the Wyoming Basin of the Northern Antra- 
cite Field. The purpose of the study was 
to evaluate the effect of mine flooding 
on AMD formation. Specific project goals 
included identification of sites where 
pyrite oxidation may still be occurring 
and mapping patterns of contaminant flow. 

Between 1980 and 1982, nine abandoned 
mine shafts were monitored for vertical 
variations in the chemical composition of 
the mine water system. Each shaft inter- 
sected several coal seams. Monitoring 



included the collection of shaft water 
samples, downhole Eh and pH measurement, 
fluid resistivity logging, spontaneous 
potential logging, and fluid tempera- 
ture logging. In addition to the shaft 
logging, the four major outfalls in the 
Wyoming Basin were monitored on a week- 
ly basis from October 1982 through Sep- 
tember 1983. These data were compared 
with available historical data for the 
outfalls. 

Water quality at the outfalls in the 
Wyoming Basin has exhibited marked im- 
provement since inundation of the mine 
complex. For example, between 1968 and 



17 



1980 sulfate concentrations decreased by 
49 pet at the Buttonwood Outfall (fig. 
3). At all of the outfalls, pH has in- 
creased to near neutral and net acidity 
has decreased. 

Weekly monitoring indicated water qual- 
ity was similar at three of the four out- 
falls (Buttonwood, South Wilkes Barre, 
and Askam) , despite large differences in 
respective recharge areas and predicted 
residence times (table 1). The similar- 
ity may reflect a long-term trend toward 
uniformity coupled with the general im- 
provement in water quality. The Nanti- 
coke Outfall, which exhibits sulfate con- 
centrations 25 to 35 pet higher than the 
other three outfalls, discharges the 
"youngest," or most recently formed, mine 
pool. If a trend toward uniformity does 
exist, the Nanticoke Outfall water qual- 
ity may be expected to improve more rap- 
idly than water quality at the other 
outfalls. 

TABLE 1. - Mean pH, sulfate, and flow 
for the four outfalls in the Wyoming 
Basin for the period October 1982 
through September 1983 



Outfall 


pH 


Sulfate, 
mg/L 


Flow, 
gal/min 


South Wilkes Barre 

Buttonwood 

Askam 


5.9 
5.9 
5.9 
6.0 


1,200 
1,020 
1,130 
1,640 


25,380 
5,690 
5,650 


Nanticoke 


2,900 



No significant seasonal trends in con- 
taminant levels were observed, despite 
order of magnitude variations in flow. 
The absence of seasonal trends again im- 
plies a uniform source. Thorough mixing 
of the surface water recharge with the 
bulk mine pool apparently occurs prior to 
outfall discharge. 

The shaft monitoring revealed marked 
changes in water quality with depth with- 
in the basin. In five of the nine shafts 
studied, water was layered into two major 
zones separated by sharp changes in Eh, 
pH, and water quality parameters. An ex- 
ample of the vertical change in pH and 
sulfate is shown in figure 4. 



The stratification appears to be re- 
lated to discharge elevations at the time 
of inundation, as well as to present 
flow conditions. In each case, the sharp 
change in water quality occurred just 
above or below seams with mined barrier 
pillars. Relative positions of mined 
barrier pillars, outfall installations, 
and natural structural features combine 
to create an environment more favorable 
to flushing in the shallower parts of the 
mine system. As a result, the least con- 
taminated water was found in the upper 
zones of the system, while the poorest 
quality was observed in flow-restricted, 
deeper zones. 

, 4,000 



3,000 - 



o 

z 
o 
o 



CO 



2,000 



1,000 - 



s 


1 


^ 


- 


^ 


t 


s 


1 

KEY 
• Mean 
I Range 

H-t- 

1 





1968 1970 



1972 1974 1976 



1978 



1980 



tr 



FIGURE 3. - Mean and range of sulfate concen- 
ations at the Buttonwood Outfall. 



Surface, 183 m 
600f— F"™ai 



500- 



400 



300 



y 200 

u 



100 



-100 



(602 ft) 
Top of rock 
Hillmcn 

Diamond 



Lance 

Top Pitlston 
Bottom Pittston 



Ross 



^•Present bottom 



Red Ash 



KEY 

« Allreodings 6/26/81 
■■■■ Coalbed not mined from shaft 
ezzz2 Coalbed mined from shaft I 



\ 



150 



100 e 



50 LJ 



800 IPOO 1,200 1,400 1,600 5 6 7 
SULFATE CONCENTRATION, mq/L pH 



FIGURE 4. - Vertical profile of pH and sulfate 
in Gaylord shaft, Wyoming Basin. 



18 



The improvement in water quality ap- 
pears to indicate a decrease or cessation 
of pyrite oxidation, along with neutrali- 
zation and flushing of preexisting con- 
taminants. The rate of flushing and min- 
imum contamination levels attainable are 
difficult to quantify, Pyrite oxidation 
is still occurring at the surface in old 
refuse piles and strip pits , and these 
oxidation products are continuously 
washed into the subsurface flow system. 
The recharging pollutants are probably 
confined to small, near-surface flow sys- 
tems and may tend to control the minimum 
contamination levels attained at the dis- 
charge points. 



In addition to the surface contami- 
nants , the reservoir of oxidation prod- 
ucts in the flooded mine complex will 
continue to discharge for many years. 
Stimulation of flow from the deep zones 
by the addition of fully penetrating dis- 
charge structures may increase the rate 
of flushing but would aggravate the pol- 
lutant load on the surface streams if 
the discharge is left untreated. The 
construction of additional outfalls would 
also lower water levels, increasing the 
unflooded volume of the mine complex and 
possibly renewing pyrite oxidation in 
these areas. 



REFERENCES 



1. Ackers, P., W. R, White, J. A. 
Perkins, and A. J. M. Harrison. Weirs 
and Flumes for Flow Measurement. Wiley, 
1978, 327 pp. 

2. Caruccio, F. T. , and G. Geidal. 
Estimating the Minimum Acid Load That Can 
Be Expected From a Coal Strip Mine. Pa- 
per in Proceedings, 1981 Symposium on 
Surface Mining, Sedimentology and Recla- 
mation, Lexington, KY, Dec. 7-11, 1981, 
ed. by D. H. Graves. Univ. KY, 1981, 
pp. 117-122. 

3. Ladwig, K, J. Use of Surface Geo- 
physics To Determine Flow Patterns in 
Surface Mine Spoil. Paper in Surface and 



Borehole Geophysical Methods in Ground 
Water Investigations (San Antonio, TX, 
Feb. 6-9, 1984). National Water Well 
Association, Worthington, OH, 1984, 
pp. 455-471. 

4. Ladwig, K. J., P. M, Erickson, 
R. L, P. Kleinmann, and E. T. Posluszny. 
Stratification in Water Quality in Inun- 
dated Anthracite Mines, Eastern Pennsyl- 
vania. BuMines RI 8837, 1984, 35 pp. 

5. Scalf, M. R. , J. F. McNabb, W. J. 
Dunlap, R. L. Cosby, and J. Fryberger. 
Manual of Ground-Water Sampling Proce- 
dures. Natl. Water Well Assoc, 1981, 
93 pp. 



19 



OXYGEN CONTENT OF UNSATURATED COAL MINE WASTE 
By Patricia M, Ericksonl 



INTRODUCTION 



Acid mine drainage (AMD) results from 
the oxidation of pyrite in the presence 
of oxygen, water, and iron-oxidizing bac- 
teria. Any of these three components 
acting on the pyrite provides a potential 
control point for reducing AMD formation. 



The purpose of this project is to deter- 
mine the oxygen availability in coal 
refuse and spoil to improve our under- 
standing of its potential to control acid 
production. 



BACKGROUND 



The overall rate of acid production 
is controlled by the rate-limiting step 
in the chemical reactions of pyrite. 
The rate dependence of pyrite oxidation 
has been investigated in the labor.atory. 
Under a variety of conditions near at- 
mospheric pressure, the pyrite oxida- 
tion rate was shown to depend on oxygen 
partial pressure at values less than 
2.0 m),2 10 (O, or 20 pet ( n_) . The 
actual rate dependence under field con- 
ditions is critical to the design of 
abatement strategies. If field acid pro- 
duction rates are a function of oxygen 
availability at all partial pressures, 
then even a limited reduction in atmos- 
pheric diffusion into the pyritic mate- 
rial will reduce the acid load. Alterna- 
tively, if oxygen is rate limiting only 
at low partial pressures, rigorous exclu- 
sion of oxygen would be required to af- 
fect acid production. 

Few reports are available on the oxygen 
status of coal refuse and spoil. Hons 
measured pore gas composition as part of 
a lignite waste revegetation study (8^). 
Jaynes (9-10) monitored oxygen and carbon 
dioxide within a backfilled surface coal 
mine and developed an acid production 



model. Other models have been presented 
by Colvin (4_) and Brown (J^) • Further 
work has been reported on metal mining 
waste products and solution mining sites 
(^-_3, 7^), Oxygen profiled tend to fall 
into two categories. Compacted materials 
tend to show decreased partial pressures 
of oxygen with increasing depth. Oxygen 
profiles of less compacted materials, 
such as heap leaching systems and coarse 
waste disposal sites, appear to be con- 
sistent with air convection through ex- 
posed faces. Actual field data on acid 
production rates and pore gas composition 
are necessary to calibrate available mod- 
els or formulate new models and to eluci- 
date the probable effects of proposed 
acid abatement strategies. 

To date. Bureau of Mines work has fo- 
cused on characterizing gas composition 
profiles in coal mine refuse and spoil. 
Water quality data are also being col- 
lected for investigation of possible cor- 
relation between acid production and oxy- 
gen availability. Preliminary findings 
were reported earlier (5) , Only the oxy- 
gen content of the pore gas is discussed 
in this paper. 



OXYGEN IN COAL REFUSE 



Four inactive coal refuse disposal 
areas, ranging in approximate age from 2 

^Supervisory physical scientist, Pitts- 
burgh Research Center, Bureau of Mines, 
Pittsburgh, PA. 



to 12 yr, were Included in the study. 
Soil gas probes ( 13) , installed to depths 

^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this paper. 



20 



of 15 to 90 cm, were sampled periodi- 
cally. Samples were analyzed by gas 
chromatography for atmospheric gases and 
low-molecular-weight hydrocarbons . 

Table 1 illustrates the range of oxygen 
concentrations found in pore gas at the 
four sites. Atmospheric oxygen levels 
(~21 pet) were generally found only in 
the uppermost 30 cm of the refuse. Val- 
ues less than 2 pet were observed at 
depths as shallow as 15 cm below the sur- 
face. Based on the lowest literature 
values (11), oxygen concentrations were 
sufficiently low at times to restrict py- 
rite oxidation. 

Long-term monitoring was conducted only 
at one site (Morgan County, OH). Figure 
1 illustrates the average pore gas oxygen 



profile generated from 12 sets of gas 
samples. This profile appears to be con- 
sistent with a model of the system based 
on oxygen diffusion from the atmosphere 
and oxygen consumption within the refuse 
by pyrite oxidation. Near-surface pyrit- 
ic material is undergoing active oxida- 
tion, evidenced by runoff acidity in the 
range of 10,000 to 20,000 mg/L. 

Gas composition in the refuse showed 
a strong seasonal dependence. Figure 2 
shows average oxygen profiles for samples 
taken in the summer and winter seasons. 
There was very little overlap between the 
data sets. During the summer, the oxygen 
profile was sharp and showed the greatest 
change within the uppermost 15 cm of ref- 
use. Oxygen was found at significant 



TABLE 1. - Range of pore gas content in coarse coal refuse 





Oxygen, moisture-free vol pet 


Depth, cm 


Allegheny County, PA 


Wise County, VA 


Morgan County, OH 




Site A 


Site B 




15 

20 


20.4-20.7 

18.9-19.9 

ND 

6.5-14.9 

ND 

ND 


ND 

20.0-20.4 

ND 

5.7-17.2 

.4- 3.5 

ND 


20.2-20.8 

ND 

9.1-20.7 

ND 

ND 

.2- 9.6 


0.3-21.8 
ND 


30 


.1-20.8 


35 


ND 


66 


ND 


90 


ND 



OXYGEN, av pet 
10 15 



20 



25 




FIGURE 1. - O2 for four sets of gas probes 
at the Morgan County, OH, site. 



E 
o 



I- 

Q. 
UJ 
Q 



OXYGEN, pet 








5 


10 15 


20 


25 


20 


1 


1 1 


^ 


- 


40 


- 




KEY \ 




- 


60 






Summer \ 
Winter \ 






80 


< 


\ 1 


, \ 


1 





FIGURE 2. - Refuse was more oxygenated at all 
probe depths in winter (December through February) 
than in summer (June through August). 



21 



concentrations at greater depths in the 
winter months. One would expect that the 
oxidation reactions occur at lower rates 
during the cold season and that the 



decreased oxygen consumption explains the 
higher oxygen content of the pore gas at 
depths up to 80 cm. 



SPOIL OXYGEN CONTENT 



We are currently monitoring pore gas 
composition in spoil at three regraded 
surface mines. Multiport gas-sampling 
wells (5) were installed at two or more 
locations on each site to monitor pore 
gas composition in the unsaturated zone. 
The oxygen profiles were distinctly dif- 
ferent from those in coal refuse at the 
Morgan County site and did not show site- 
to-site consistency. Oxygen concentra- 
tions of 5 to 20 pet occurred to depths 
of several meters and, in some cases, 
throughout the unsaturated zones. 

Figure 3 shows the average oxygen pro- 
file obtained from seven gas-sampling 
wells at an unvegetated site in Clarion 
County, PA. Overall, the oxygen content 
of the gas decreased with depth. Howev- 
er, the zones of greatest change in oxy- 
gen content differed for individual wells 
on the 11-acre site (fig. 4). Seasonal 
trends have not been examined yet. 



Figure 5 shows the average oxygen pro- 
files for three wells at a recently re- 
vegetated site in Upshur County, WV. 
This isolated ridge was reclaimed accord- 
ing to state-of-the-art guidelines, in- 
cluding the selective placement of toxic 
spoil above a nonreactive base pad and 
below a compacted clay cap (6^) . Gas- 
sampling wells were placed parallel to 
the ridge axis at approximately equal 
spacing. Sampling ports were located as 
follows: in the soil, in the top, mid- 
dle, and bottom of the acidic spoil zone, 
and in the base pad. Two of the wells 
showed decreasing oxygen with increasing 
depth, while the third well showed a peak 
oxygen content in the middle of the 
acidic spoil zone (fig. 5). The greatest 
change in oxygen for a given change in 
depth occurred in the acidic spoil zone 
of wells 847 and 846 and between the soil 
and acidic spoil zones for well 793. The 
high oxygen values at the 5.9-m depth in 



OXYGEN, av pet 
10 15 



OXYGEN, avpct 



20 



25 




FIGURE 3. - Oj profile from seven gas-sampling 
wells at the Clarion County, PA, site. 



2- 



CL 
LlI 
Q 



6- 



8 





5 


10 15 20 


25 


- 


I 

c 


1 1 1/ 
y^ KEY 


- 


c/ 


1 ^ 


'^ o Well 1 
o Well 11 

1 1 1 





FIGURE 4. - Oj profiles for two of seven gos- 
sampling wells at the Clarion County, PA, site. 
The change in Oj pet varied for the same depth 
interval. 



22 







X 

I- 

Q. 
UJ 
Q 



10 



15 



OXYGEN, av pet 
5 10 15 20 



25 




KEY 

Well 847 
Well 793 
Well 846 



FIGURE 5. - Oj profiles for three gas-sampling 
wells at the reclamation study site in Upshur 
County, WV. 



OXYGEN, av pet 
10 15 



20 25 




FIGURE 7. - Oj profiles in revegetated spoil 
at the abandoned site in Upshur County, WV. 




ASONDJ FMAMJ J 
1983 1984 

TIME, months 

FIGURE 6. - Variation in oxygen content 2 ft 
below the compacted clay layer at the reclaimed 
study site in Upshur County, WV. 

well 847 may be due to the location of 
the well on the exposed end of the mined 
ridge. Well 847 is surrounded by steep 
slopes on three sides as compared to 
slopes on two sides for the other wells. 



The clay cap was placed over the acidic 
spoil to minimize rainfall infiltration 
(6^). We also thought it might act as 
a diffusion barrier. Figure 6 summa- 
rizes the preliminary data available from 
the air well ports located 0.6 m beneath 
the clay cap. There appeared to be a 
distinct seasonal increase in oxygen dur- 
ing the spring and summer. The changing 
oxygen levels indicate that the clay lay- 
er is not a good diffusion barrier. 

The third site, also located in Upshur 
County, WV, is an abandoned, revegetated 
surface mine. A three-port gas well (No. 
8) was installed adjacent to buried py- 
ritic material, which has been identified 
as the major source of acid drainage on 
the site. A four-port well (No. 5) was 
placed in the outslope area, which is 
composed of rocky spoil. Figure 7 shows 
the average profiles for both wells. 
Well 8 data indicated a steep decrease in 
oxygen content within the uppermost 1.8 m 
of spoil. Well 5 showed a different type 
of oxygen profile, not consistent with 
vertical downward diffusion. The loca- 
tion of well 5 on the outslope may ac- 
count for this observation; diffusion 



and/or convection may occur along the 
outslope face or toe. Similar profiles 



23 



have been observed in coarse mining waste 
rock (7). 



DISCUSSION 



Pore gas oxygen content in coal refuse 
generally decreased to only a few percent 
within 1 ra below the surface at four un- 
vegetated sites. According to most lit- 
erature reports, a lower limit of 1 or 2 
pet oxygen could be used to define the 
pyrite-oxidizing zone. In that case, the 
bulk refuse should not be contributing 
much to the acid load at these sites. 
However, in the winter months oxygen lev- 
els greater than 15 pet were observed at 
greater depths. In the absence of con- 
sumption in the shallow zone, oxygen 
would be available to oxidize pyrite at 
greater depths. Cover with a nonpyritic 
coal refuse would probably not reduce the 
acid load. Coal mine spoil would proba- 
bly be an ineffective cover material for 
the same reason: At the three sites we 
studied, the spoil pore gas usually con- 
tained sufficient oxygen to support py- 
rite oxidation. 

Coal mine spoil oxygen profiles showed 
great variety among sites and laterally 
on a single site. In 10 of 12 wells at 
3 sites, oxygen usually decreased with 
depth. These profiles are consistent 
with oxygen diffusion from the atmosphere 
downward through the spoil. The notable 
exceptions were the outslope area at the 
abandoned site and the exposed end of the 
ridge at the recently reclaimed site. 
Profiles from these two areas were simi- 
lar to profiles observed in coarse waste 
subject to air convection through exposed 
slopes ( 7_) . 

Gas composition monitoring can provide 
useful information about the location of 
pyrite oxidation zones. The steep gradi- 
ent observed in the summer in coal refuse 
apparently is indicative of a zone of ac- 
tive oxidation. Similar zones in mine 
spoil, in the absence of a change in dif- 
fusion coefficient with depth, may also 
be indicators of pyrite oxidation. For 



example, well 8 at the abandoned West 
Virginia site showed a steep gradient and 
is known to be adjacent to a mass of 
buried pyritic material currently produc- 
ing acid. Identification of acid source 
areas will allow application of remedial 
treatments to selected zones, thereby re- 
ducing cost. 

The seasonal trends in oxygen profiles 
are not consistent. We observed peaks in 
oxygen concentrations during the winter 
in coal refuse and during the summer in 
one spoil site. The winter peaks suggest 
that the refuse is more oxygenated when 
chemical activity decreases due to lower 
temperatures. We do not know why peak 
oxygen levels were observed in the summer 
at the spoil site. 

The results reported in this paper sug- 
gest that inert cover materials may not 
be useful as diffusion barriers to reduce 
pyrite oxidation. Covering the pyritic 
refuse or spoil with an oxygen-consuming 
layer is probably a better control strat- 
egy. Vegetation, soil containing an ac- 
tive microbial population, and decaying 
organic matter are candidate cover mate- 
rials. We are planning to conduct tests 
this year to evaluate the effects of veg- 
etation and mulch on pore gas profiles in 
coal refuse. Previously reported revege- 
tation studies have generally neglected 
measuring oxygen availability; instead, 
the plant growth and water quality were 
usually monitored. Measurements of gas 
diffusion rates are also needed to deter- 
mine the flux of oxygen through the waste 
materials. 

Future work will also include appli- 
cation of available computer models to 
fit the field data. The best-fit model 
will then be used to assess the proba- 
ble impacts of proposed acid abatement 
techniques , 



24 



REFERENCES 



1. Brown, W. E. The Control of Acid 
Mine Drainage Using an Oxygen Diffusion 
Barrier. M.S. Thesis, OH State Univ., 
1970, 86 pp. 

2. Cathles , L. M. Predictive Capabil- 
ities of a Finite Difference Model of 
Copper Leaching in Low Grade Industrial 
Sulfide Waste Dumps. Math. Geol, , v. 11, 
1979, pp. 175-191. 

3. Cathles, L. M. , and J. A. Apps. A 
Model of the Dump Leaching Process That 
Incorporates Oxygen Balance, Heat Balance 
and Air Convection. Metall. Trans. B, v. 
6B, 1975, pp. 617-624. 

4. Colvin, S. L. Oxygen Diffusion in 
Strip-Mined Soils. M.S. Thesis, lA State 
Univ., Ames, lA, 1977, 72 pp. 

5. Erickson, P. M. , R. L. P. Klein- 
mann, W. R. Homeister, and R. C. Briggs. 
Reclamation and the Control of Acid Mine 
Drainage. Paper in Proceedings, Sympo- 
sium on the Reclamation, Treatment and 
Utilisation of Coal Mining Wastes. Na- 
tional Coal Board (United Kingdom), 1984, 
pp. 30.1-30.18. 

6. Geidel, G. , and F. T. Caruccio. A 
Field Evaluation of the Selective Place- 
ment of Acidic Material Within the Back- 
fill of a Reclaimed Coal Mine. Paper in 
Proceedings, 1984 Symposium on Surface 
Mining, Hydrology, Sedimentology , and 
Reclamation, Lexington, KY, Dec. 2-7, 
1984, ed. by D. H, Graves. Univ. KY, 
1984, pp. 127-131. 

7. Harries, J. R. , and I. A. M. Rit- 
chie. The Effect of Rehabilitation on 



the Oxygen Concentrations in Waste Rock 
Dumps Containing Pyritic Material. Paper 
in Proceedings, 1984 Symposium on Surface 
Mining, Hydrology, Sedimentology, and 
Reclamation, Lexington, KY, Dec. 2-7, 
1984, ed. by D. H. Graves. Univ. KY, 
1984, pp. 463-466. 

8. Hons , F. M. Chemical and Physical 
Properties of Lignite Spoil Materials and 
Their Influence Upon Successful Reclama- 
tion. Ph.D. Thesis, TX A&M Univ. , 1978, 
137 pp. 

9. Jaynes , D. B. , A. S. Rogowski , and 
H. B. Pionke. Acid Mine Drainage From 
Reclaimed Coal Strip Mines. I. Model 
Description. Water Resour. Res., v. 20, 
1984, pp. 233-242. 

10. Jaynes, D. B. , A. S. Rogowski, 
H. B. Pionke, and E. L. Jacoby, Jr. At- 
mosphere and Temperature Changes Within 
Reclaimed Coal Strip Mine. Soil Sci., v. 
136, 1983, pp. 164-177. 

11. Morth, A. H. , E. E. Smith, and 
K. S. Shumate. Pyritic Systems: A Math- 
ematical Model. EPA-R2-72-002, 1972, 
169 pp. 

12. NUS Corporation. The Effects of 
Various Gas Atmospheres on the Oxidation 
of Coal Mine Pyrites. EPA 14010 ECC, 
1971, 140 pp. 

13. Staley, T. E. A Point-Source 
Method for Sampling Soil Atmospheres. 
Trans. Am. Soc. Agri. Eng. , v. 23, 1980, 
pp. 578-580, 584. 



25 



CONTROL OF ACID MINE DRAINAGE BY APPLICATION OF BACTERICIDAL MATERIALS 

By Patricia M. Erickson,'' Robert L. P. Kleinmann,2 
and Steven J, Onysko-^ 



INTRODUCTION 



The kinetics of acid formation are de- 
pendent on the availability of oxygen, 
the surface area of pyrite exposed, the 
activity of iron-oxidizing bacteria, and 
the chemical characteristics of the in- 
fluent water. The principal iron-oxidiz- 
ing bacterium involved in accelerating 
pyrite oxidation is Thiobacillus f erro- 
oxidans (9^, _1_5).^ The Bureau of Mines 
has previously reported the results of 



full-scale field tests that showed how 
anionic surfactants (cleansing deter- 
gents) can be used to reduce the activity 
of T. ferrooxidans (12-13) and thereby 
abate acid formation. After a brief dis- 
cussion of the literature, this paper 
will review the surfactant solution tech- 
nique and report progress on two alterna- 
tive procedures. 



ACKNOWLEDGMENTS 



The controlled release surfactant 
formulations were provided by BFGood- 
rich and Granger Technologies, Inc. The 



assistance of both companies is grate- 
fully acknowledged. 



BACKGROUND INFORMATION 



The possible involvement of bacteria in 
the formation of acid drainage was first 
reported in 1919 by Parr and Powell, who 
determined that coal inoculated with an 
unsterilized ferrous sulfate solution 
produced drainage with higher concen- 
trations of sulfate than did sterile 
controls (J^) . The possibility of reduc- 
ing acid drainage by bacterial inhibition 
was first considered in 1953 but was re- 
jected as impractical due to probable 
rapid repopulation (14) . Later labora- 
tory studies demonstrated the vulnerabil- 
ity of T^ ferrooxidans in coal and coal 
refuse to anionic surfactants and conse- 
quent acidity reductions of 65 to 80 pet 
(7). 



Supervisory physical scientist. 



^Research supervisor. 

^Civil engineer. 
Pittsburgh Research Center, Bureau of 
Mines, Pittsburgh, PA. 

^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this paper. 



Full-scale tests at active and inactive 
coal refuse areas demonstrated that sodi- 
um lauryl sulfate (SLS) surfactant appli- 
cation could effectively reduce acid pro- 
duction and thereby lower water treatment 
costs. Sufficient surfactant was applied 
by hydroseeder to the coal refuse to sat- 
urate the adsorptive capacity of the top 
1 ft of refuse, based on a laboratory de- 
termination (13). The 1-ft-thick treat- 
ment zone was selected for several rea- 
sons: (1) Oxidation was assumed to occur 
largely in a near-surface oxygenated zone 
(3, 6), (2) desorption and downward mi- 
gration would result in treatment at 
greater depth, and (3) it was preferred 
to undertreat rather than overtreat, to 
prevent significant surfactant concentra- 
tions off the site. 

Water quality improved at the test 
sites in 1 to 3 months. Acidity, sul- 
fate, and manganese decreased 60 to 90 
pet; iron decreased 90 to 95 pet (fig. 
1). After about 4 months, contaminant 
concentrations slowly climbed back to 



26 



E 



o 

01 



UJ 

o 



5,000 



4,000 



3,000 



2,000 



8 1,000 








KEY 

-X Acidity 



A A Sulfate 

o o Iron 






.-A 
— X 



^t=^-^» ^^-:---.v-4>-K>-^i-o-<> 



40 60 80 100 120 140 

TIME AFTER TREATMENT, days 



160 180 



FIGURE 1. - Improvement in drainage quality following surfactant solution application at a site in 
West Virginia. 



previous levels. Effluent surfactant 
concentrations were negligible. 

As a result of these tests, the mining 
industry has begun to apply surfactants 
to coal refuse, coal stockpile areas, un- 
reclaimed mine spoil, and waste sulfide 
rock, with mixed results. One coal com- 
pany that applied an anionic surfactant 
two or three times a year to a developing 
coal refuse pile has had no acid problem 
over a 5-yr period despite the fact that 
coal refuse at the plant typically pro- 
duces acidic drainage within 6 months. 
At the other extreme are sites where the 
technique produced no apparent effect or 
only a short-term improvement in water 
quality. Some of these failures can be 
explained simply, such as when the dosage 
rate or site conditions were obviously 
inappropriate. At other sites it may 
never be known why the technique failed 
to reduce acid production. 

A previous report describes in some de- 
tail when and how the surfactant should 



be applied (13) . It is worthwhile to re- 
state the three most significant points: 

1. Determine beforehand if the tech- 
nique is potentially cost effective for 
the site. Assume a material cost of 
$600/ acre annually plus the cost of three 
applications by watering truck or hydro- 
seeder, a 60-pct decrease in neutraliza- 
tion costs, and a 90-pct decrease in 
sludge accumulation; if the calculated 
annual savings are not significantly 
greater than the assumed costs , the tech- 
nique is probably not appropriate. 

2. The surfactant must reach and ad- 
sorb to the pyritic material. If the 
site is covered with topsoil, a surfac- 
tant application will not reach the py- 
ritic material and will therefore accom- 
plish nothing. If an adsorption test 
indicates that the pyritic material has 
low adsorptive capacity, the surfactant 
will wash away rapidly, providing only 
brief abatement. 



27 



3. Owing to slow hydrologic flow- 
through time or pooled acid water on the 
old mine floor or in a refuse area, the 
effect of surfactant treatment may be de- 
layed, masked, or made insignificant. In 
the case of slow flow-through time (as 
much as a year at some sites), improve- 
ment in water quality at the discharge 
point cannot occur faster than water 
flows through the material. If a signif- 
icant pool of acid water exists, years of 
continued application of surfactant could 
be required before an increase in water 
quality is observed, unless the acid pool 
is first neutralized or drained. 

Application of anionic surfactant solu- 
tion, although effective in reducing wa- 
ter treatment costs, cannot be regarded 
as a long-term control measure. Two mod- 
ifications of the basic approach are be- 
ing considered by the Bureau of Mines: 



1. The surfactant can be rendered less 
soluble. This has been accomplished us- 
ing slow-release technology developed for 
more conventional biocides (2^, 10) . Con- 
trolled release of surfactant over a pe- 
riod of many years may be possible. 

2. Other environmentally safe chemi- 
cals have been identified that inhibit T. 
f errooxidans and that react with acid 

to form slightly soluble 

Thus, these chemicals may 

material in 



mine drainage 

precipitates . 

form their own slow-release 

the acid-producing environment . 



The remainder of this paper will summa- 
rize the results of laboratory and pilot- 
scale experiments and introduce full- 
scale field tests that are in progress. 



SLOW RELEASE OF SURFACTANTS 



This approach has been under investiga- 
tion since surfactants were first con- 
sidered for field use (7). Early surfac- 
tant-rubber formulations reduced acid 
formation by over 95 pet in a pilot-scale 
field test but were effective for less 
than 1 yr (8^) . Subsequent research has 
been directed towards extending the re- 
lease lifetime of the material and field 
tests of the resultant formulations. 

LABORATORY TESTS 



and surface area, 
dissolution. 



influenced the rate of 



Laboratory and pilo 
been conducted on more 
manufactured for the 
and Granger Technologi 
manufactured prior to 
SLS as the active ingr 
sitions are propriet 
are referred to in thi 
betic code. 



t-scale tests have 
than 20 materials 
tests by BFGoodrich 
es . The materials, 
1982, all contained 
edient. The compo- 
ary , and materials 
s report by alpha- 



Laboratory tests were conducted ini- 
tially to determine which variables most 
strongly influenced the SLS release rates 
(_H_) . Every parameter investigated, in- 
cluding nature of matrix, SLS loading, 



Figure 2 shows release curves for five 
formulations for illustrative purpose. 
The data were obtained by periodically 
rinsing a 5-g sample with 100 mL deion- 
ized water. Leachates were combined to 
400 to 500 mL total volumes and analyzed 
for anionic surfactants by the methylene 
blue method (J_) . The percent SLS remain- 
ing in the matrix was calculated from the 
nominal SLS content of the sample and the 
cumulative mass of SLS extracted. Nomi- 
nal SLS contents, ranging from 20 to 65 
pet of the total sample weight, were nor- 
malized to 100 pet for comparison. 

All formulations exhibited an initial 
rapid release of detergent followed by 
a slower dissolution phase. The first 
phase was more pronounced in samples hav- 
ing a larger fraction of SLS at or near 
the pellet surface. For example, samples 
D and E are cylindrical pellets of the 
same formulation having diameters of 4.6 
and 3.2 mm, respectively. Approximately 
three times more detergent was dissolved 



28 




< 

Q 
CO 
UJ 

cr 



60 



KEY 

X Formulation A 
D Formulation B 
^ Formulation C 
O Formulation D 
A Formulation E 







I 2 3 

CUMULATIVE LEACH VOLUME, L 

FIGURE 2. - SLS release curves for five control led 
release formulations subjected to intermittent leach 
ing in the laboratory. 



from sample E than from sample D in the 
first liter of leach water (fig. 2), 

Under the experimental conditions 4,000 
mL is approximately equivalent to 40 in 
of precipitation. Cumulative extracted 
SLS at this point ranged from 4 to 38 pet 
of the total surfactant content of the 
samples. These values cannot be extrapo- 
lated to an expected lifetime, however, 
because release rates were decreasing 
over time. In some formulations much of 
the detergent appeared to be unavailable 
(curves D and E of figure 2). 

While the laboratory results confirmed 
that surfactant loading, pellet geometry, 
and matrix type affected SLS release 
rates, no empirical equations could be 
developed to predict release curves for 
new formulations. Outdoor evaluation of 
potential materials was considered pre- 
ferable to continued laboratory testing. 

PILOT- SCALE TESTS 

Pilot-scale testing was conducted out- 
doors to determine release rates under 
field conditions. The test area con- 
sisted of two small coal refuse piles, 



each about 7 ft wide, 12 ft long, and 1.5 
ft high at the lengthwise crest. Garden 
edging was used to divide each slope into 
six test plots. A rain gage was placed 
about 15 ft from the refuse piles. 

Approximately 250 to 500 g of pellets 
were spread by hand on each of 21 test 
plots during February 1983. The coal 
refuse contained about 5 pet sulfur and 
produced drainage acidity on the order 
of 10^ mg/L prior to the controlled re- 
lease application. No attempts were made 
to monitor drainage quality during the 
experiment. 

Periodically, a selected number of pel- 
lets were removed at random from each 
plot and residual SLS content was deter- 
mined. In one method, the samples were 
dried to constant weight at room tempera- 
ture, and SLS release was calculated by 
weight loss: 

SLS release = nominal weight 

- actual weight 

This method is based on the assumption 
that all weight loss resulted from SLS 
dissolution. Nominal weights were deter- 
mined as the mean weight of 10 repli- 
cate samples of fresh pellets of the same 
formulation. 

The second method involved aqueous ex- 
traction of residual SLS from air-dried 
samples. The pellets were placed in a 
minimum of 500 mL deionized water and al- 
lowed to equilibrate for several days. 
The extracts were analyzed for anionic 
surfactants, and the extracted pellets 
were air-dried for determination of ma- 
trix weight. This method was based on 
the assumption that all residual SLS 
could be extracted into deionized water. 
Values were calculated from actual dry 
matrix weight and nominal dry matrix 
weight. A typical release curve is shown 
in figure 3 for a formulation nominally 
containing 50 pet SLS by weight. Three 
calculation methods used to determine 
residual SLS content usually yielded re- 
sults that agreed to within 10 pet. This 



29 




2 4 6 8 10 12 
CUMULATIVE PRECIPITATION, in of rain 

FIGURE 3. - SLS release curve from the outdoor 
pilot-scale test. Formulation was approximately 
50 wt pet SLS. Multiple data points were calcu- 
lated using weight loss and extraction data. 

large variation is due to the indirect 
measurements mentioned previously. The 
curves generally followed the same pat- 
tern observed in the laboratory study 
(fig. 2), although SLS release was much 
more rapid in the field. 

Table 1 shows the residual SLS content 
for all the formulations after 11 in of 
precipitation. Essentially all the sur- 
factant dissolved from nine of the sam- 
ples within the 4-month period repre- 
sented by the tabulated results. Seven 
of these samples were composed of early 
matrix formulations. At the other ex- 
treme, two samples released essentially 
none of the surfactant during the pilot- 
scale test. Several formulations exhib- 
ited release rates (residual SLS 65 to 90 
pet) that might provide the desired re- 
lease lifetime of several years. 

Negative numbers on table 1 resulted 
when some of the weight loss assumed to 
be SLS dissolution was actually loss of 
matrix. Some of the thinner rubber ma- 
trices underwent significant degradation 
that produced visible shrinkage of the 
pellets. All samples tested in the 



TABLE 1. - Residual SLS after exposure 
of formulations to 11 in of precip- 
itation on coal refuse test piles 



Plot 

No 



SLS CO 


ntent , 


pet 


of 


init 


ial' 



1... 


-2 


12... 


-15 


2... 


12 


13... 


18 


3... 


27 


14... 


20 


4... 


-14 


15... 


-7 


5... 





16... 


98 


6.. 


-16 


17... 


65 


7.. 


-8 


18.. 


20 


8.. 


-5 


19.. 


47 


9.. 


16 


20.. 


125 


10.. 


-18 


21.. 


83 


11.. 


90 







Plot SLS content, 
No 



pet of 
initial 1 



to 



Initial SLS content, ranging from 20 
65 pet, was normalized ' to 100 pet. 



laboratory and in the pilot-scale test 
exhibited much higher SLS dissolution 
rates in the latter ease. Exposure to 
ultraviolet light and moist, acidic ref- 
use probably contributed to faster re- 
lease through degradation of the ma- 
trices. Burial of the controlled release 
pellets beneath a soil cover should re- 
tard release rates by reducing degrada- 
tion and limiting contact with rainfall. 

FIELD PROJECTS 

The Bureau is participating in one 
field trial of the controlled release 
concept (_5 ) . The site is a 15-acre iso- 
lated ridge in Upshur County, WV, which 
was mined and reclaimed in three sec- 
tions. State-of-the-art reclamation 
techniques, including a clay cap emplaced 
over the toxic material, were used (19). 
Surfactant solution and a controlled re- 
lease surfactant formulation were applied 
to one section below the clay layer. 
Since completion of reclamation during 
spring 1983, seeps and surface runoff 
have been monitored. To date, the post- 
mining hydrology has not developed suf- 
ficiently to allow characterization of 
drainage quality from the various 
sections . 



30 



Selection of the controlled release 
material was based on early laboratory 
data; we now know that the surfactant is 
released from the matrix in less than 1 
yr when the pellets are applied to the 
surface of acidic material. Exposed to 
no sunlight and less water under the clay 
cap, detergent release should be signifi- 
cantly slowed. 

Both Goodrich and Granger are now de- 
veloping new formulations to optimize 
surfactant release rates. The former 
company is currently conducting field 
tests of 1984 formulations that we have 
not tested (4). In the oldest test, the 
controlled release pellets were applied 
during summer to a portion of a coal ref- 
use site prior to application of seed and 
soil to the entire site. At the end of 
the first growing season, there was good 
vegetation cover on the treated refuse, 
compared with extensive acid burnout 
areas on the untreated portion. 



precipitates when added to synthetic AMD 
in the pH range of 4 to 5. The precipi- 
tates probably consist of ferric or fer- 
rous salts of the organic acids. Further 
testing was encouraged by the fact that 
these organic acids are used as food and 
beverage preservatives and hence should 
be environmentally safe. 

Laboratory tests of bacterial inhibi- 
tion have previously been reported (18) . 
In solution cultures of a pure strain of 
T. f errooxidans , bacterial activity was 
monitored as the utilization of ferrous 
iron in the medium. The bacteria derive 
energy from oxidation of ferrous iron. 
Figure 4 illustrates the results in unin- 
hibited bacteria culture, in sterile me- 
dium, and in two bacterial cultures con- 
taining benzoic acid. We found that 10 
mg/L of either benzoic or sorbic acid was 
sufficient to decrease the rate of fer- 
rous iron oxidation to that of sterile 
controls. 



ORGANIC ACID INHIBITORS 



PILOT-SCALE TESTS 



We began to investigate another alter- 
native for control of T. f errooxidans 
when the limitations of the solution sur- 
factant technique became apparent. For 
materials having low affinity for sur- 
factant and sites having high water 
flow rates, a less soluble inhibitor was 
needed. The concept was to identify 
organic compounds with the following 
properties: 

1 . Toxic to T^ ferrooxidans but innoc- 
uous to other organisms . 

2. Sparingly soluble in AMD or neu- 
tralized mine drainage. 

3. Actively bactericidal once redis- 
solved or in response to acid production. 

Preliminary experiments consisted of a 
survey of 25 organic compounds , which 
might be inhibitors and which might pre- 
cipitate as sparingly soluble compounds 
in AMD, These experiments yielded two 
candidate compounds: sodium benzoate and 
potassium sorbate. We found that O.l-pct 
solutions of either salt formed organic 



Bactericidal effectiveness of potas- 
sium sorbate, sodium benzoate, and SLS 
was investigated for reducing acid pro- 
duction from fresh and weathered refuse; 



CJ> 



O 
(f) 

3 
O 

cc 

DC 
UJ 



10 




12 3 4 5 6 

TIME, weeks 

FIGURE 4. - Ferrous iron oxidation by T. ferro- 
oxidans , as function of added benzoic acid. The 
sterile culture indicates the rate of abiotic 
oxidation. 



31 



preliminary results have been published 
previously (17) . 

Drums filled with 200 kg of fresh coal 
refuse were leached weekly by saturating 
the material for 24 h with tap water. 
The drained leachate was analyzed for pH, 
acidity, total dissolved iron, and sul- 
fate. In the first week of the experi- 
ment, 24 L of inhibitor solution replaced 
the water in six of the drums. The three 
inhibitors were each tested at concentra- 
tions of 500 and 5,000 mg/L (equivalent 
to 60 and 600 mg chemical per kilogram 
of refuse) . Ten drums of refuse were 
"treated" with tap water and used for ex- 
perimental control. 

The low doses of treatment chemicals 
were marginally effective, delaying acid 
production 1.5 to 5 weeks after leachate 
from the control barrels became acidic 
(fig. 5). High treatment doses of 5,000 
mg/L were effective for 8 to 10 weeks 
(fig. 6). Potassium sorbate yielded the 
best results in both treatment series. 

At low dosage rate, sorbate was least 
expensive on the basis of cost per week 
of delayed acidification. However, at 
the high dosage rate, the duration of the 
treatments were more similar and the 



chemical of choice would probably depend 
on cost per pound. Approximate bulk 
prices are $0.90/lb for sodium benzoate, 
$1.67/lb for SLS, and $3.52/lb for potas- 
sium sorbate. Field trials will be re- 
quired before an accurate cost analysis 
can be made. The longevity of SLS treat- 
ment under field conditions is about 
twice as great as in the high-dosage 
pilot-scale test; the experimental condi- 
tions of extremely high leaching rates 
probably underestimate the duration of 
all three inhibitors. 

After 22 weeks of weathering, 9 of the 
10 control barrels were treated with the 
chemical inhibitors to determine their 
effectiveness in the highly acidic envi- 
ronment of aged refuse. Drainage acidity 
levels were approximately 8,000 to 14,000 
mg/L at the start of this experiment. 
During the 22-week leaching program, 
drainage from the untreated barrel re- 
tained as a control became 70 pet less 
contaminated. The easily oxldizable py- 
rite may have been consumed during the 
initial 22 weeks of weathering; cumula- 
tive sulfate load data indicated approxi- 
mately 10 pet of the total pyrite had 
been oxidized before treatments were ap- 
plied to the aged refuse. 



"5 

c 
o 

o 
o 

E 

jj 

O 
O 

o 



9 

o 

< 



10 



KEY 

Control 



Sodium lauryl sulfate 

Potassium sorbate 

Sodium benzoate 








25 



5 10 15 

TIME, weeks 

FIGURE 5, - Acidity levels in leachate from cool 
refuse treated witfi 500 mg/L of chemical inhibitor. 



D 

c 
o 

o 
o 

E 

o 
o 

CO 

o 



en 

t 
g 

< 



10 



KEY 
Control 

Sodium lauryl sulfate 
Potassium sorbate 
Sodium benzoate 




re 



fu 



5 10 15 

TIME, weeks 

CURE 6.- Leachate acidity from fresh cool 
se treated with 5,000 mg/L of chemical inhibitor. 



32 



15 



KEY 

Control 

Sodium lauryl sulfate 

Potossium sorbate 

- Sodium benzoate 




20 



25 



5 10 15 
TIME, weeks 

FIGURE 7. • Effect of low doses of treatment 
chemicals on weathered coal refuse leachate 
compared with leachate from untreated refuse. 

Superimposed on the trend of decreasing 
contaminant concentrations, additional 
improvements in drainage quality were ob- 
served (figs. 7-8). At the low dosage 
rate of 500 mg/L, only potassium sorbate 
produced significantly better drainage 
than did the control. All three chemi- 
cals were effective at the 5,000-mg/L 
dosage rate. Cumulative acid loads (fig. 
9) were 17, 29, and 38 pet lower for so- 
dium benzoate, potassium sorbate, and SLS 
treatments, respectively, at the end of 
22 weeks than in the control drainage. 
Seven weeks after treatment, when the in- 
hibitors were most effective, cumulative 
acid loads were 45 to 62 pet lower in the 
high treatment dose leachates than in the 
control leachate. 

A field test is now in progress at a 
revegetated mine site in West Virginia. 
Dry potassium benzoate powder was applied 
to the surface on 2 acres overlying the 
major acid-producing zone. Water quality 
is being monitored in the vadose zone, in 



o 
c 
o 
J2 



15 



KEY 

Control 



Sodium lauryl sulfate 

Potassium sorbate 

— Sodium benzoate 




^n; 



20 



5 10 15 

TIME, weeks 

FIGURE 8. - High doses of three treatment 
chemicals reduced acidity of weathered coal 
refuse leachate, compared to leachate of un- 
treated coal refuse. 



25 




10 15 

TIME, weeks 



20 



25 



FIGURE 9. - Cumulative acidity produced by weath- 
ered cool refuse after application of high doses of in- 
hibitory chemicals. Curve symbols as in figure 8. 

the saturated zone, and at the discharge 
seep. 



SUMMARY 



Preliminary experiments were conducted 
on two alternatives to the surfactant so- 
lution technique for controlling acid 



drainage. Controlled release of sur- 
factants appears to be a feasible means 
of extending the bactericide lifetime. 



Further work, in the form of field tests, 
is needed to determine the cost effec- 
tiveness of this method. 

The organic Inhibitors , benzoate and 
sorbate, were of the same general order 
of effectiveness as surfactant solution 
in pilot-scale tests. There may be some 



33 



cost advantage in using benzoate; a field 
test of this compound is in progress. 
Under moderately acidic conditions where 
adsorption is unlikely, such as in some 
underground mines, the metal-organic salt 
precipitate may have further advan- 
tages in extending the duration of acid 
control. 



REFERENCES 



1. American Public Health Association. 
Standard Methods for the Examination of 
Water and Waste Water. 13th ed., 1971, 
874 pp. 

2. Cardarelli, N. Controlled Release 
Pesticide Formulations. CRC Press, 
Cleveland, OH, 1976, 224 pp. 

3. Erickson, P. M. , R. L. P. Klein- 
mann, and P. S. A. Campion. Reducing 
Oxidation of Pyrite Through Selective 
Reclamation Practices. Paper in Proceed- 
ings, 1982 Symposium on Surface Mining 
Hydrology, Sedimentology , and Reclama- 
tion, Lexington, KY, Dec. 6-10, 1982, 
ed. by D. H. Graves. Univ. KY, 1982, 
pp. 97-102. 

4. Fox, L. A., and V. Rastogi. Devel- 
opments in Controlled Release Technology 
and Its Application in Acid Mine Drain- 
age. Paper in Proceedings, 1983 Symposi- 
um on Surface Mining, Hydrology, Sedi- 
mentology, and Reclamation, Lexington, 
KY, Nov. 27-Dec. 2, 1983, ed. by D. H. 
Graves. Univ. KY, 1983, pp. 447-455. 

5. Geidel, G. , and F. T. Caruccio. A 
Field Evaluation of the Selective Place- 
ment of Acidic Material Within the Back- 
fill of a Reclaimed Coal Mine. Paper in 
Proceedings, 1984 Symposium on Surface 
Mining, Hydrology, Sedimentology, and 
Reclamation, Lexington, KY, Dec. 2-7, 
1984, ed. by D. H. Graves. Univ. KY, 
1984, pp. 127-131. 

6. Good, D. M. , V. T. Ricca, and K. S. 
Shumate. The Relation of Refuse Pile Hy- 
drology to Acid Production. Paper in 
Preprints of Papers Presented Before the 
Third Symposium on Coal Mine Drainage 



Research (Pittsburgh, PA, May 19-20, 
1970). Mellon Inst., Pittsburgh, PA, 
1970, pp. 145-151. 

7. Kleinmann, R. L. P. The Biogeo- 

chemistry of Acid Mine Drainage and a 

Method To Control Acid Formation. Ph.D. 

Thesis, Princeton Univ., Princeton, NJ, 
1979, 104 pp. 



8. 



Bactericidal Control of 



Acid Problems in Surface Mines and Coal 
Refuse. Paper in Proceedings, 1980 Sym- 
posium on Surface Mining, Hydrology, Sed- 
imentology, and Reclamation, Lexington, 
KY, Dec. 1-5, 1980, ed. by D. H. Graves. 
Univ. KY, 1980, pp. 333-337. 

9. Kleinmann, R. L. P., and D. A. 
Crerar. Thiobacillus f errooxidans and 
the Formation of Acidity in Simulated 
Coal Mine Environments. Geomicrobiol. 
J., V. 1, 1979, pp. 373-388. 

10. Kleinmann, R. L. P., D. A. Crerar, 
and R. R. Pacelli. Biogeochemistry of 
Acid Mine Drainage and a Method to Con- 
trol Acid Formation. Min. Eng., v. 33, 

1980, pp. 300-306. 

11. Kleinmann, R. L. P., and P. M. 
Erickson. Field Evaluation of a Bacteri- 
cidal Treatment To Control Acid Drainage. 
Paper in Proceedings, 1981 Symposium on 
Surface Mining Hydrology, Sedimentology, 
and Reclamation, Lexington, KY, Dec. 7- 
11, 1981, ed. by D. H. Graves. Univ. KY, 

1981, pp. 325-329. 



12. 



Full-Scale Field Trials of 



a Bactericidal Treatment To Control Acid 
Mine Drainage. Paper in Proceedings, 
1982 Symposium on Surface Mining 



34 



Hydrology, Sedimentology , and Reclama- 
tion, Lexington, KY, Dec. 6-10, 1982, ed. 
by D. H. Graves. Univ KY, 1982, pp. 617- 
622. 

13. Kleinmann, R. L. P. , and P. M. 
Erickson. Control of Acid Mine Drainage 
From Coal Refuse Using Anionic Surfac- 
tants. BuMines RI 8847, 1983, 16 pp. 

14. Leathen, W. W. The Influence of 
Bacteria on the Formation of Acid Mine 
Drainage. Abstracted in Coal and the En- 
vironmental Abstract Series: Mine Drain- 
age Bibliography, ed. by V. Gleason and 
H. H. Russell. Bituminous Coal Research, 
Monroeville, PA, 1976, 288 pp. 

15. Leathen, W. W. , S. Braley, Sr. , 
and L. D. Mclntyre. The Role of Bacteria 
in the Formation of Acid From Certain 
Sulfuritic Constituents Associated With 
Bituminous Coal. Part 2. Ferrous Iron 
Oxidizing Bacteria. Appl. Microbiol. , v. 
1, 1953, pp. 65-68. 

16. Lorenz , W. C. , and R. W. Stephan. 
Factors That Affect the Formation of Coal 
Mine Drainage Pollution in Appalachia. 



Attachment C. Appendix C, Acid Mine 
Drainage in Appalachia. Appalachian Re- 
gional Committee, Washington, DC, 1969, 
21 pp. 

17. Onysko, S. J., P. M, Erickson. 
R. L. P. Kleinmann, and M. Hood. Control 
of Acid Drainage From Fresh Coal Refuse: 
Food Preservatives as Economical Alterna- 
tives to Detergents. Paper in Proceed- 
ings, 1984 Symposium on Surface Mining, 
Hydrology, Sedimentology, and Reclama- 
tion, Lexington, KY, Dec. 2-7, 1984, ed. 
by D. H. Graves. Univ. KY, 1984, pp. 35- 
42. 

18. Onysko, S. J. , R. L. P. Kleinmann, 
and P. M. Erickson. Ferrous Iron Oxida- 
tion by Thiobacillus f errooxidans : Inhi- 
bition With Benzoic Acid, Sorbic Acid, 
and Sodium Lauryl Sulfate. Appl. and En- 
viron. Microbiol., v. 28, No. 1, July 
1984, pp. 229-231. 

19. West Virginia Acid Mine Drainage 
Task Force. Suggested Guidelines for 
Method of Operation in Surface Mining of 
Areas With Potentially Acid-Producing Ma- 
terials. 1979, 20 pp. 



35 



ALKALINE INJECTION: AN OVERVIEW OF RECENT WORK 



By Kenneth J. Ladwig, ^ Patricia M, Erick.son,2 and Robert L. P. Klei 



nmann- 



INTRODUCTION 



Injection of alkaline fluid into sur- 
face mine spoil to control acid mine 
drainage (AMD) is a procedure generating 
considerable interest in Pennsylvania. 
At least six different mine companies or 
contractors have attempted some form of 
injection in the last 2 yr, and many more 
are considering its use. This paper 
gives a brief overview of the current 
status of alkaline injection and of the 
Bureau of Mines injection research. 

Introduction of alkalinity is the stan- 
dard method of mitigating acid dis- 
charges. Surface alkaline loading prior 
to flow through the spoil has been used 
to slow down the acid-production process 
ii_, ^) • ^ More commonly, alkalinity is 
added to the discharge to neutralize ex- 
isting acidity with conventional water 
treatment (4). 



decreasing sludge storage 
requirements. 



and removal 



2. The metal precipitates may coat py- 
rite surfaces, "armoring" them from fur- 
ther chemical weathering, 

3. The alkaline environment within the 
spoil would be less favorable to contin- 
ued pyrite oxidation. 

4. The high-pH environment would limit 
metal leaching within spoil. 

5. Spoil water that "leaks" through 
the mine floor discharges to the ground 
water system untreated. Alkalinity in- 
troduced into the spoil water reservoir 
may offer at least partial treatment of 
the leakage and decrease overall ground 
water degradation. 



The premise of alkaline injection is 
the in-place neutralization of acid water 
stored in the spoil. In this respect, 
alkaline injection is not much different 
than conventional water treatment. Alka- 
line materials that have been used for 
injection are sodium hydroxide, hydrated 
lime, and sodium carbonate, all of which 
are commonly used in AMD water treatment. 
Some of the potential advantages of in- 
jection over conventional water treatment 
follow: 

1. Raising the pH of the spoil water 
may result in the precipitation and fil- 
tering of some metals prior to discharge, 



6. Treatment by alkaline injection 
could be done on an intermittent basis, 
lowering labor costs. 

While the premise of alkaline injection 
is straightforward, implementation is 
not. The extent to which any of the 
above listed advantages are realized is 
not known. Of the six attempts with 
which we are familiar, none have yet sub- 
stantially improved spoil seep water 
quality. Unfortunately, documentation of 
these injections was generally incom- 
plete. For this reason, the Bureau ini- 
tiated a study to evaluate the technical 
merit of the injection approach. 



^Hydrologist. 

^Supervisory physical science, 

•^Research supervisor. 
Pittsburgh Research Center, Bureau of 
Mines, Pittsburgh, PA, 

^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this paper. 



Described in the following section are 
two injection programs for which a rea- 
sonable amount of documentation was 
available. At the Fayette site, the Bu- 
reau monitored the results of an injec- 
tion performed by Kaiser Refractories, 
Much of the data were generously supplied 
by Bernard Leber of Kaiser Aluminum and 
Chemical Corp, and Mike Popchak of the 



36 



Kaiser Refractories division. Descrip- 
tions and data for the Clearfield site 
were kindly provided by Jim McNeil of 



Al Hamilton Contracting Co. Bureau re- 
search on alkaline injection is described 
in the final section. 



EXAMPLES OF ALKALINE INJECTIONS 



FAYETTE COUNTY, PA 

A lime slurry injection project was 
conducted at a surface mine in Fayette 
County in 1983. The lU-ha Fayette site 
was mined at various times between the 
mid-1950 's and late 1970 's. At present, 
about one-half of the site has been re- 
vegetated (fig. 1). Spoil thickness 
ranges from 15 to 30 m. 

The site has several toe-of-spoil seep- 
age areas, one of which (seepage area A, 
figure 1) discharges directly onto the 
flood plain of a small, perennial stream. 
Seepage area A has two major seeps, 16 
and 18. The proportion of flow from each 
of these seeps varied throughout the 
study, but in 1983, flow at seep 18 was 
generally much higher than at seep 16. 
Owing to steep topography and space limi- 
tations, installation of conventional 



treatment facilities and settling ponds 
between seep area A and the stream was 
considered impractical. 

In February 1983, Kaiser initiated an 
injection program in seepage area A. 
Fifteen injection wells were installed 
approximately 90 m up gradient from the 
seepage area (fig. 1). The wells were 
drilled an average of 18 m to the mine 
floor. Two-inch-diameter polyvinyl chlo- 
ride well pipe was placed in each hole 
and cemented at the surface. The lower 
16 m of the pipes were perforated with 
0.32-cm holes. Water levels were 3 to 
5 m above the mine floor. 

Between February and October 1983, 
119 tons of hydrated lime were pumped 
into the wells in slurry form. The 
slurry concentration ranged from 4 pet 
lime during the early stages of injection 




Scale, m 



FIGURE 1. - Map of surface mine study site in Fayette County, PA. 



37 



to 0.4 pet during the latter stages. In- 
jections were performed weekly at a rate 
of 7 to 42 tons of lime per week. 

The transit time from the injection 
wells to seepage area A was estimated by 
analyzing the movement of a sodium tracer 
in the lime slurry (fig. 2). The first 
arrival of the injected sodium at seepage 
area A was about 4 months after the be- 
ginning of the injection. Peak concen- 
trations occurred 7 to 9 months after the 
beginning of the injection. Concentra- 
tions began tailing off following the 
cessation of injection in October. Peak 
sodium concentrations at the seeps indi- 
cated a 1:3 ratio of injected water to 
spoil water. 

Trends in pH and acidity for seeps 16 
and 18 are shown in figures 3-6. Although 
very few pre-injection data were avail- 
able, there did appear to be a modest im- 
provement at seep 16 beginning about 7 
months after the initial injection. The 
pH at seep 16 increased by 1/4 to 1/2 of 
a pH unit, while the acidity decreased by 
30 to 40 pet. However, no significant 
changes in water quality were observed at 
seep 18. As seep 18 comprises a larger 
percentage of the total flow from seepage 
area A, the overall impact of the injec- 
tion was minimal. 




1983 

FIGURE 2. 
and 17. 



19&4 

SAMPLE DATE 



1985 



- Sodium concentrations at seeps 16 



Assuming complete reaction, 119 tons of 
lime is capable of neutralizing 36 mil- 
lion gal of water with an average acidity 
of 1,000 mg/L. Because the total dis- 
charge from seepage area A in 1983 was 
less than 20 million gal, the high lime 
dosage should have had a profound impact 
on seep quality. 

The explanation of the poor results may 
lie in the inefficient mixing of the lime 
with the spoil water. The solubility of 
lime in deionized water is 1,600 mg/L at 
20<^ C (1). Saturation with respect to 
lime would produce a solution of 0.16 pet 
dissolved lime. Because the lime slurry 
was mixed at concentrations of 0.4 to 
4 pet, 60 to 95 pet of the lime was in 
suspension rather than solution. At a 
treatment plant using mixers to induce 
turbulent flow, much of ' the suspended 
lime might eventually contact acidic 
water and participate in the neutraliza- 
tion reactions. However, the injected 
fluid was not subjected to continuous 
turbulent flow and very likely did not 
mix efficiently with the spoil water. In 
the absence of turbulence and mixing, 
suspended lime will settle rapidly. En- 
hanced solution will occur only along the 
slurry-spoil water contact surface, con- 
siderably slowing the rate of lime con- 
sumption. As a conservative estimate, 
over 50 pet of the 119 tons of lime at 
the Fayette site may have settled out of 
suspension shortly after injection. 

The lime remaining in solution mixed 
with the spoil water at a 1:3 dilution 
rate at the peak injection period, as 
previously determined from the sodium 
data. Assuming an initial concentration 
of 1,600 mg/L dissolved lime in the in- 
jection fluid, the maximum lime concen- 
tration following 1:3 mixing with the 
spoil water is 400 mg/L. This amount of 
lime is capable of neutralizing only 
490 mg/L acidity. 

These calculations are intended to il- 
lustrate in a general sense the controls 
placed on the system by the solubility of 
lime and the low velocity of ground water 
flow. Although these numbers are in 



38 




1983 



1985 



1984 

SAMPLE DATE 

FIGURE 3. - Seep 16 pH. Lime injection began 
in February 1983. 



1J500 



1,400 



1^00 



800 



400 




1983 



1984 

SAMPLE DATE 



1985 



FIGURE 4. - Seep 16 acidity. 




1983 



1984 
SAMPLE DATE 



1985 



FIGURE 5. - Seep 18 pH. Lime injection began 
in February 1983. 



1400 



1^00- 



600 




1983 



1984 

SAMPLE DATE 



1985 



FIGURE 6. - Seep 18 acidity. 



reasonable agreement with the data from 
seep 16, they do not explain why no 
change was observed at seep 18. Ongoing 
work at the site is designed to better 
describe the hydrologic differences be- 
tween the two seeps. 

CLEARFIELD COUNTY, PA 

A hydrated lime injection program is 
also being conducted by a mine company 
at a site in Clearfield County, PA. The 



approach taken at the Clearfield site was 
similar to that described for the Fayette 
site. In June 1982, 22 injection wells 
were drilled an average of 15 m to the 
mine floor. The wells were located about 
75 m upgradient of the toe-of-spoil seep. 
Approximately 3,000 gal of 4-pct lime 
slurry are pumped into each well on a 
monthly basis from April through Novem- 
ber. Due to cold temperatures, no injec- 
tions occur between December and March. 



39 



Preliminary data indicate that toe-of- 
spoil seeps at the Clearfield site have 
not exhibited appreciable improvement 
since injection began. However, dovm- 
stream monitoring does indicate improve- 
ment in the receiving stream. In the 
last 2 yr, there have been reductions in 
acidity and iron concentrations at the 
downstream monitoring station. 

The lack of improvement at the toe- 
of-spoil seeps may again be a result of 
the low solubility of lime, as described 
for the Fayette site. Why then did the 
downstream water quality improve? 

Owing to other modifications in the 
watershed contemporaneous with the 



injection, it is not possible at this 
time to attribute the downstream water 
quality improvement solely to the injec- 
tion program. If the improvement is re- 
lated to the injection, it may reflect an 
improvement in ground water quality below 
the mine floor. Stored spoil water leak- 
ing through the mine floor may contain 
a high alkaline load following contact 
with the settled lime. The mine water 
recharges the underlying ground water 
system and eventually discharges by dif- 
fuse seepage to the receiving stream, 
resulting in improved water quality down- 
stream from the site. While this is 
purely conjecture at this time, the down- 
stream water quality improvement cer- 
tainly merits further study. 



BUREAU OF MINES INJECTION PROJECT 



The widespread interest in injection 
technology, along with the limited suc- 
cess to date, prompted a Bureau of Mines 
study of the injection approach. While 
alkaline injection is not a cure-all for 
AMD problems at surface mines , the se- 
lective use of injection in combination 
with other abatement procedures may offer 
several benefits. Possibly the most 
valuable potential benefit is the renova- 
tion of contaminated ground water below 
the mine floor, a problem not currently 
addressed by any other treatment 
technology. 

Critical to the success of alkaline in- 
jection is good mixing of the alkaline 
fluid and the contaminated spoil water. 
This requires detailed understanding of 
site hydrology and acid-producing charac- 
teristics, including source material, 
flow paths, flow rates, flow volumes, and 
spoil-water chemistry. We believe that 
inadequate mixing, largely due to the low 
solubility of lime and low flow veloc- 
ities, was one of the primary shortcom- 
ings of the previous injection attempts. 
Our approach will differ from these at- 
tempts in two ways. 

First, sodium carbonate solution will 
replace lime slurry as the alkaline 



fluid. Sodium carbonate is about 100 
times more soluble than lime (2^) , allow- 
ing mobility of a greater fraction of the 
alkaline load. The concentration of the 
sodium carbonate solution will be select- 
ed to maximize alkaline loading with min- 
imal density contrasts between the in- 
jected fluid and the spoil water. 

Second, injection wells will be situ- 
ated at least 300 m upgradient from the 
seep to enhance dispersion of the inject- 
ed fluid. Dispersion in porous media is 
directly related to distance along the 
flow path ( O • Placing the injection 
wells on the upgradient end of the site 
will allow for maximum mechanical disper- 
sion of the alkaline fluid. This will 
also minimize the possibility of the al- 
kaline fluid migrating directly to the 
seep as an unreacted plume. Monitoring 
wells will be sampled to track the prog- 
ress of the injected fluid in the 
spoil. 

Bureau work to date has consisted of 
pilot-scale testing of lime and sodium 
carbonate, and preliminary site evalua- 
tion for a full-scale field test. In the 
pilot-scale tests, sodium carbonate was 
considerably more mobile than lime. The 
full-scale field test began in spring of 



40 



1985 at the Fayette County site described 
earlier. 

In addition to the field test, we hope 
to conduct laboratory column studies to 
simulate and study in detail the reac- 
tions between the injected fluid and 



spoil water. In particular, we are in- 
terested in observing the reaction prod- 
ucts — gaseous, aqueous, and solid — and 
evaluating their effect on the metal ion 
chemistry and pyrite oxidation system. 
This work is tentatively scheduled to be- 
gin by mid-1985. 



REFERENCES 



1. Caruccio, F. T. , and G. Geidel. 
Induced Alkaline Recharge Zones to Miti- 
gate Acidic Seeps. Paper in Proceedings, 
1984 Symposium on Surface Mining, Hydrol- 
ogy, Sedimentology , and Reclamation, Lex- 
ington, KY, Dec. 2-7, 1984, ed. by D. H. 
Grover. Univ. of KY, 1984, pp. 43-48. 

2. Freeze, R. A., and J. A. Cherry. 
Groundwater. Prentice-Hall, 1979, pp. 
388-413. 

3. Neast, R. C. (ed.). Handbook of 
Chemistry and Physics. CRC Press, 53d 
ed., 1972-73, pp. B-77 and B-137. 



4. U.S. Environmental Protection Agen- 
cy. Design Manual: Neutralization of 
Acid Mine Drainage. EPA-6001Z-83-001, 
1983, 231 pp. 

5. Waddell, R. K. , R. R. Parizek, and 
D. R. Buss. The Application of Limestone 
and Lime Dust in the Abatement of Acidic 
Drainage in Centre County, PA. PA Dep. 
Trans. Office Res. and Spec. Studies, 
Project 73-9, Final Report — Executive 
Summary, 1980, 79 pp. 



41 



COMPARATIVE TESTS TO ElEMOVE MANGANESE FROM ACID MINE DRAINAGE 

By George R. Watzlaf ' 

INTRODUCTION 



The Surface Mining Control and Recla- 
mation Act of 1977 mandates that mine 
drainage discharge water meet qual- 
ity standards for pH, iron, manganese, 
and total suspended solids (11).^ These 
standards are shown in table 1. Typical 
treatment of acid mine drainage involves 
addition of an alkaline material (such 
as lime or sodium hydroxide) , natural or 
mechanical aeration, and settling. When 
mine drainage is neutralized to a pH near 
7, the ferrous iron oxidizes and forms an 
iron sludge, Fe(0H)3. This treatment 
satisfies the effluent standards for pH 
and iron, but may not remove much manga- 
nese from the water. 

Typical acid mine drainage contains 1 
to 8 mg/L manganese, but concentrations 
of 50 to 100 mg/L are not uncommon {6_, 
9). At present, most mine operators with 
manganese problems are using excess alka- 
linity to raise pH of the mine water to 

^Mining engineer. Pittsburgh Research 
Center, Bureau of Mines, Pittsburgh, PA. 

^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this paper. 



about 10.0 to precipitate manganese. 
During the precipitation of manganese, as 
Mn02, acid is produced and the pH of the 
water decreases. Whether or not the pH 
will fall below 9.0 depends on individual 
mine water characteristics. If the pH 
remains above 9.0 the mine operator has 
two options: apply to State autorities 
for a variance to discharge high-pH wa- 
ter, or reacidify the high-pH water. An 
alternative to excess alkalinity is the 
use of chemical oxidants such as chlorine 
gas, hypochlorite salts (sodium and cal- 
cium), ozone, potassium piermanganate, or 
hydrogen peroxide (^-^> 9^). These oxi- 
dants can oxidize soluble manganese 
to insoluble Mn02 ^t pH values within the 
regulatory criteria. 

Based on a review of the literature on 
manganese removal, three chemical treat- 
ments were selected for field testing: 
excess alkalinity, sodium hypochlorite, 
and potassium permanganate. The selec- 
tion of these treatment methods was based 
on ease of use, costs (capital and oper- 
ating), availability, effectiveness, and 
likelihood of acceptance by the mining 
industry. 



TABLE 1. - Effluent limitations 





Maximum 
allowable 


Av 


erage of daily values 
for 30 consecutive 
discharge days 


Iron, total 




• .me /L . . 


7.0 

4.0 

70.0 

6.0-9.0 






3.5 


Mflnganp^Pj ^n^fl^ , , 




. .m2 /L. . 


2.0 


Total suspended so 
pH 


lids. 


. .mg/L. . 


35.0 
6.0-9.0 



42 



EXTENT OF MANGANESE IN ACID MINE DRAINAGE 



Mine drainage discharges that require 
treatment for removal of manganese are 
widespread throughout the Eastern U.S. 
coalfields. A study of mine discharges 
containing manganese was conducted by 
Pennsylvania's Department of Environmen- 
tal Resources for Jefferson, Clearfield, 
Clinton, Venango, and Clarion Counties. 
This study found manganese concentrations 
averaging 75 mg/L and ranging from 20 to 
170 mg/L. In southwestern Pennsylvania, 
mining of the Waynesburg seam can result 
in manganese concentrations over 200 
mg/L. In eastern Kentucky manganese con- 
centrations of 10 to 100 mg/L are common. 
Mine discharges in southern Illinois typ- 
ically have 5 to 10 mg/L of manganese, 
but values in excess of 300 mg/L have 
been reported (_5) . 

Sodium hypochlorite solution is being 
used to remove manganese from mine drain- 
age in eastern Kentucky. Two sites were 
visited used a combination of sodium hy- 
pochlorite and sodium hydroxide. At one 
site, the operator initially used calcium 
hypochlorite briquettes but had dif- 
ficulty controlling the quantity of chem- 
ical added to the system. At the other 
treatment facility, a flocculant was 



required to achieve adequate settling of 
the precipitated sludge. 

Potassium permanganate has been used to 
treat mine drainage at a site in Pennsyl- 
vania. Granular potassium permanganate 
was added directly to the sodium hydrox- 
ide solution. The operator at this site 
achieved good results for a few months 
but had difficulty maintaining the proper 
dosage. The operator is now using excess 
alkalinity to remove manganese. 

Bureau personnel visited two sites in 
Pennsylvania that use the excess alkalin- 
ity method for removal of manganese. One 
operator uses sodium hydroxide in liquid 
form, and the other adds hydrated lime 
via a flash mixer. At both sites the op- 
erators add alkali to raise pH to about 
10.0 and discharge at a pH near 9.0. 

With adequate control, all three treat- 
ment methods can be effective in reducing 
manganese concentrations below effluent 
limitations. To directly compare the 
costs and effectiveness of these methods, 
they must be used to treat the same mine 
water. 



CHEMISTRY OF MANGANESE REMOVAL 



The chemistry for removing manganese 
with pH adjustment is very similar to 
that of iron removal, but oxidation of 
Mn^"*" to Mn^"*" requires higher pH values 
than are required for iron oxidation. To 
remove manganese, the following two re- 
actions are promoted: 

Mn2+ + 1/2 O2 + 2H+ ^ Mn"*-^ + H2O (1) 

Mn"^"^ + 2H2O ->■ Mn02 + 4H+ (2) 

The rate of manganese oxidation is pH 
dependent and extremely slow at pH val- 
ues less than 8.0. Reduction of man- 
ganese concentrations below 2 mg/L 
can occur at pH 8.4 (8^), but most mine 
drainages require pH values over 9.5 (_5, 
7-9). 



To remove manganese at near-neutral pH, 
a chemical oxidant must be used. Oxi- 
dizing agents commonly used in water 
treatment include chlorine, sodium hypo- 
chlorite, calcium hypochlorite, potassium 
permanganate, hydrogen peroxide, and 
ozone. The following reactions show how 
sodium hypochlorite (NaOCl) and potassium 
permanganate (KMn04) each oxidize dis- 
solved manganese (Mn^"*") and convert it to 
manganese oxide (Mn02): 

NaOCl + Mn2+ + H2O 

->■ Mn02 + Na+ + CI" + 2H"^ (3) 
2KMn04 + 3 Mn2+ + 2H2O 

-J- 5 Mn02 + 2K+ + 4H+ (4) 



43 



Because these chemicals will oxidize 
both Fe'^2 3nd Mn"^^ in acid mine drainage, 
it is reasonable to first oxidize Fe^"*", 
by increasing pH and aerating, before 
adding an oxidizing agent. This reduces 
the requirement for the chemical oxidant 
and lowers costs. Also, some manganese 
is removed by coprecipitation with iron 
even at near-neutral pH, by sorbtion to 
Fe(0H)3 {]_) , further reducing the chemi- 
cal oxidant requirement. 

FIELD 



Regardless of the method used, control- 
ling the addition of chemical treatment 
is very important. Many variables influ- 
ence the removal of iron and manganese, 
and experimentation with different chemi- 
cal dosages may be required to achieve 
optimal results. As the quantity and 
quality of AMD change, the dosage of the 
treatment chemical must change to ensure 
effective manganese removal. 

TESTS 



The purpose of the field tests was to 
determine the most economic chemical 
treatment that would successfully reduce 
manganese concentrations below 2 rag/L. 
All testing was conducted at the same 
surface mine site in southwestern Penn- 
sylvania. Based on ease of use, costs 
(capital and operating), availability, 
effectiveness, and likelihood of accept- 
ance by the mining industry, sodium hypo- 
chlorite, potassium permanganate, and ex- 
cess alkalinity were chosen for field 
testing. 

The field site is an active surface 
mine with over half of the site mined and 
reclaimed. Existing treatment consists 
of sodium hydroxide (NaOH) addition with 
two settling ponds connected in series 
(fig. 1). Raw water contains concentra- 
tions of manganese consistently over 100 
mg/L. Flow at this site is seasonal and 
averaged 40 gal/min during the testing 
period. 

Three series of tests were conducted. 
In all tests, the raw water was first 
treated with NaOH for pH adjustment 
and some iron oxidation before adding 
any other chemicals. Series 1 used chem- 
ical dosages based on reaction stoichio- 
metry for complete removal of manganese 
and iron. Series 2 used varying amounts 
of each chemical treatment to determine 
the minimum dosage required to reduce 
manganese below 2 mg/L. The water in 
series 2, which was first neutralized 
with NaOH, still contained high fer- 
rous iron concentrations. Therefore, 
series 3 tests repeated the procedure of 
series 2, but used additional aeration to 
reduce iron levels before further chemi- 
cal treatment. Reduced iron levels were 



Seep 



Raw 
water 




i Pond 2- 




Final 
effluent 



FIGURE 1. - Water treatment 
system at field site. 



44 



expected to lower the chemical require- 
ments for sodium hypochlorite and potas- 
sium permanganate. 

All costs presented in this study were 
based on bulk purchases of each chemical, 
including delivery. The costs for 20- 
pct sodium hydroxide and 15-pct sodium 
hypochlorite solutions were $0.28/ gal 
and $0.80/gal, respectively. The cost 
for granular potassium permanganate was 
$1.34/lb. 

SERIES 1 

In these tests, theoretically calcu- 
lated dosages of the three chemical 
treatments were used to determine if they 
would effectively reduce manganese con- 
centrations below 2 mg/L. Raw water was 
first treated with NaOH to raise pH to 
8.8 with some of the precipitated solids 
settling in pond 1 (fig. 1). The quality 
of the raw water and water after the ini- 
tial NaOH treatment and settling is shown 
in table 2. 

TABLE 2. - Water quality for test 
series 1 

After 





initial 


Raw 


NaOH 


water 


treatment 



pH 5.3 

Acidity (as CaC03) 

mg/L.. 53.0 
Alkalinity (as CaC03) 

mg/L.. 

Fe + 2 mg/L.. 230 

Total Fe mg/L.. 230 

Mn mg/L.. 120 



8.8 



82 

92 

160 
97 



Sodium hypochlorite, potassium perman- 
ganate, and sodium hydroxide were added 
as 10-, 3-, and 20-pct solutions, respec- 
tively, at point B (fig. 1). Each chem- 
ical was gravity-fed from 55-gal drums 
through plastic tubing. Dosage was reg- 
ulated with a polyvinyl chloride needle 
valve. Samples were collected in a 
5-gal container at point C (fig. 1). 
This container was then partially sub- 
mersed in pond 2 (to maintain pond tem- 
perature) and left to settle for 23 h. 
After the settling period, samples of 
the supernatant liquid were taken and 
analyzed. 

Series 1 consisted of six tests: two 
controls, two excess alkalinity, one so- 
dium hypochlorite, and one potassium per- 
manganate. Table 3 shows the results of 
these tests. Iron was reduced below ef- 
fluent standards in all six tests. The 
two controls did not reduce manganese be- 
low effluent limitations, but some man- 
ganese was removed, probably by sorbtion 
to Fe(0H)3. Also, some manganese oxida- 
tion may have occurred since pH in these 
tests was 8.4 and 8.6. The tests involv- 
ing additional chemical treatment all 
reduced manganese concentrations below 
2 mg/L. 

The cost of each chemical treatment 
(table 3) indicates that excess alkalin- 
ity was the most cost-effective method in 
this series. However, the dosages of 
NaOCl and KMn04 used in these tests may 
have been greater than the actual minimum 
effective dosage. Series 2 tests were 
performed to determine these minimum 
chemical requirements. 



TABLE 3. - Results of test series 1 



Test 


Water quality after 
23 h of settling 


Chemical cost per 




pH 


Total Fe, 
mg/L 


Mn, 
mg/L 


1,000 gal of water 


Control 1 


8.6 
8.4 
11.0 
9.4 
8.1 
7.0 


0.1 
1.2 
.6 
.6 
.6 
.8 


16 

27 

.6 

1.1 

.7 

1.2 


$1.06 


Control 2 


.80 


Excess alkalinity 1 (to pH 11.3) 
Excess alkalinity 2 (to pH 10.3) 
Sodium hvDOchlorite. •.••.••..... 


1.55 
1.31 
2.28 


Potassium permanganate 


4.49 



45 



SERIES 2 

This series of tests consisted of try- 
ing several dosages of the three treat- 
ment chemicals. As in series 1, raw 
water was first treated with NaOH to 
raise pH. After the raw water was treat- 
ed with NaOH, ferrous iron concentrations 
remained high. This was caused by inade- 
quate aeration and the short detention 
time of pond 1. The quality of the water 
used for this series of tests is shown in 
table 4. 

TABLE 4. - Water quality for test 
series 2 after initial NaOH 
treatment 

pH 9.0 

Alkalinity (as CaC03) mg/L. . 110 

Fe"'^ mg/L.. 88 

Total Fe mg/L. . 140 

Mn mg/L. . 78 



20 



^ 15 


- 




^ 


Q 


o 


\ 


z 


\ 


o 


) 


^ 10 


9 A 


UJ 




A 


en 






LU 






2 






g 


\ 







KEY 
o Potassium permanganate 
A Sodium hypochlorite 
D Excess alkalinity 




2 3 4 
TOTAL CHEMICAL COSTS 



PER 1,000 GAL OF WATER, dollars 

FIGURE 2. - Te^t series 2: Costs of chemical 
treatments versus manganese cbncentrations after 
23 h of settling. 



Twenty-three 400-mL samples were col- 
lected at point C (fig. 1). Three sam- 
ples were used as controls. The remain- 
ing 20 were treated as follows: 6 dif- 
ferent dosages of NaOCl, 6 different 
dosages of KMn04, and 8 different dosages 
of NaOH to raise pH between 9.4 and 10.5. 
These samples were left to settle for 23 
h, after which the supernatant liquid was 
analyzed. 

The results of these tests are sum- 
marized in figure 2. This graph plots 
total chemical cost versus the concentra- 
tion of manganese remaining in solution 
after 23 h of settling. Included in each 
chemical cost is the cost for the initial 
NaOH treatment ($0.83/1,000 gal). 

As in series 1 tests, excess alkalinity 
proved to be the most cost-effective 
method. Ferrous iron concentrations of 
88 mg/L may have caused an increase in 
demand for NaOCl and KMn04. It was de- 
cided to try another series of tests to 
determine the effects of lower ferrous 
iron concentrations. 

Series 3 

In these tests, raw water was collected 
at the seep (point /. of figure 1). NaOH 
was added to the raw water to raise pH to 
7.5. This water was then aerated by 



100 



£ 
(J 
o 



80 



60 



UJ 

UJ 40 



< 



20- 







KEY 
° Potassium permanganate 
A Sodium hypochlorite 
□ Excess alkalinity 




2 3 4 5 
TOTAL CHEMICAL COSTS 

PER 1,000 GAL OF WATER, dollars 

FIGURE 3. - Test series 3: Costs of chemical 
treatments versus manganese concentrations after 
23 h of settling. 

pouring it from one bucket to another, 
causing iron to oxidize and precipitate 
and pH to decrease. The procedure of 
neutralization and aeration was repeated 
until pH stabilized at 7.5. Analysis 
showed that ferrous iron concentrations 
were reduced to approximately 1 mg/L (ta- 
ble 5). Treatment chemicals were then 
added to this water, which was low in 
ferrous iron. 



46 



TABLE 5. - Water quality for test 
series 3 after initial NaOH 
treatment and induced aeration 

pH 7.5 

Alkalinity (as CaC03) mg/L. . 21 

Acidity (as CaC03) mg/L.. 5.0 

Fe+2 mg/L. . 0. 9 

Total Fe mg/L.. 3.7 

Mn mg/L. . 95 

Twenty 400-mL samples were collect- 
ed and treated as follows: one con- 
trol, seven NaOCl-treated samples, six 



KMn04-treated samples, and six excess 
NaOH samples with pH raised to between 
9.2 and 10.5. The samples were left to 
settle for 23 h. The supernatant liquid 
was sampled and analyzed. 

The results of these tests are shown in 
figure 3. Again the cost of the initial 
NaOH ($0.36/1,000 gal) was added to each 
cost. As in the first two series of 
tests, the most cost-effective method was 
excess alkalinity. The removal of fer- 
rous iron did not reduce the chemical re- 
quirements for the NaOCl and KMn04. 



DISCUSSION AND SUMMARY 



Excess alkalinity was the least expen- 
sive method to remove manganese from acid 
mine drainage. Any alkaline material 
capable of raising pH above 10 can effec- 
tively remove manganese. One drawback of 
the excess alkalinity method is that the 
final effluent may not meet effluent lim- 
itations (pH less than 9.0). The mine 
operator must get a variance in order to 
discharge high-pH water. If a variance 
to discharge high-pH water is not grant- 
ed, the operator has to either add acid 
to lower pH or use an oxidizer such as 
NaOCl or KMn04. 

Sodium hypochlorite was more expensive 
than excess alkalinity but less expensive 
than potassium permanganate. Sodium hy- 
pochlorite is commercially sold as a 15- 
pct-available-chlorine solution. This 
solution can be easily introduced into 
the treatment system. A disadvantage of 
sodium hypochlorite is that it loses 
potency with age. The 15-pct-available- 
chlorine is guaranteed 10 pet by time of 
delivery, and additional storage can lead 
to further reduction in strength. An- 
other disadvantage is the possibility of 
residual chlorine in the effluent, which 
may be regulated by State agencies. 

Potassium permanganate was the most ex- 
pensive of the three chemical treatments. 
An advantage of potassium permanganate is 
that it acts as a color indicator for 
correct dosage. KMn04 is sold in nugget 
or granular form, and if KMn04 is to be 
added as a solution, the diluting and 



mixing must be done on site. It is im- 
portant not to add too much KMn04, since 
an excess will increase manganese concen- 
trations. This effect is shown in fig- 
ures 2 and 3, where manganese concentra- 
tions increase when excess permanganate 
is added. 



In all three treatments, controlling 
chemical dosage is very important. In 
addition to wasting money, adding too 
much chemical can have other deleterious 
effects. In the case of excess alkalin- 
ity, an overdose can result in very high 
pH values. An overdose of NaOCl can re- 
sult in residual chlorine. An overdose 
of KMn04 will result in more, not less. 



CO CK 
O LlI 



o 



X < 
O CD 

_l o 
< o 

LlI 
Q. 



I - 




Initial NaOH. 



UJ O 



Initial NaOH: 



;— \ 

'ON 



o o 

UJ o 



nitial NaOH: 



SERIES 1 



SERIES 2 



SERIES 3 



FIGURE 4. - Chemical costs to reduce manganese 
concentrations below 2 mg/L. 



47 



manganese in solution. On the other 
hand, using too little of any of the 
three chemicals will result in discharg- 
ing water that exceeds effluent limita- 
tions for manganese. 

Cost comparison of the three treatments 
in each series of tests to reduce man- 
ganese concentrations below 2 mg/L is 
shown in figure 4. Excess alkalinity was 
the least expensive method of manganese 
removal, costing an average of $1 per 
1,000 gal of water treated. Although 



these chemical costs were less than half 
of those for both sodium hypochlorite and 
potassium permanganate, this method is 
still quite expensive. At this site, the 
chemical costs of the excess alkalinity 
method to remove manganese were approxi- 
mately twice the costs to treat the AMD 
for neutralization and iron removal. 
Elsewhere in these proceedings other AMD 
treatment and abatement methods are pre- 
sented. The in-line system, in particu- 
lar, has shown the potential to be an in- 
expensive method to remove manganese. 



REFERENCES 



1. Clark, J. W. , W. Viessman, Jr., and 
M. J. Hammer. Water Supply and Pollution 
Control. Harper and Row, 1977, pp. 444- 
447. 

2. Environmental Protection Agency. 
Innovative and Alternative Technology 
Assessment Manual. 1978, 443 pp. 

3. . Onsite Wastewater Treatment 

and Disposal Systems. Design Manual, 
1980, 392 pp. 

4. Evangelow, V. P. Controlling Iron 
and Manganese in Sediment Ponds. Recla- 
mation News and Views (Univ. KY) , v. 2, 
No. 1, 1984, pp. 1-6. 

5. Hood, W. C. , and S. M. Stepusin. 
Manganese Content of Some Southern Illi- 
nois Shales and Its Relation to Acid Mine 
Drainage Problems. Abstract in Program 
and Abstracts, Clay Mineral Conference. 
Clay Miner. Soc. Axinu. Meeting, Cleve- 
land, OH, Oct. 5-10, 1974, p. 35. 

6. Kim, A. G. , B. S. Heisey, R. L. P. 
Kleinmann and M, Deul. Acid Mine Drain- 
age: Control and Abatement Research. 
BuiMines IC 8905, 1982, 22 pp. 



7. Marshall, K. C. Biogeocheraistry 
of Manganese Minerals. Ch. in Biogeo- 
chemlcal Cycling of Mineral-Forming Ele- 
ments, ed, by P. A. Trudinger and D, J. 
Swaine. Elsevier, 1979, pp. 253-292. 

8. Nicholas, G. D. , and E. G. Foree. 
Chemical Treatment of Mine Drainage for 
Removal of Manganese to Permissible Lim- 
its. Paper in Proceedings, 1979 Sym- 
posium on Surface Mining, Hydrology, Sed- 
imentology, and Reclamation, Lexington, 
KY, Dec. 4-7, 1979, ed. by S. B. Carpen- 
ter. Univ. KY, 1979, pp. 181-187. 

9. Patterson, J, W. Wastewater 
Treatment Technology. Ann Arbor Science, 
1975, 265 pp. 

10. Rozelle, R. B., and H. A. Swain, 
Jr. Removal of Manganese From Mine 
Drainage by Ozone and Chlorine. EPA 
Technol. Ser. EPA 670/2-75-006, 1975, 
47 pp. 

11. U.S. Code of Federal Regulations. 
Title 30 — Mineral Resources; Chapter 
VII — Office of Surface Mining Reclamation 
and Enforcement, Department of the Inte- 
rior; Subchapter B — General Performance 
Standards; Part 715 — General Performance 
Standards. July 1, 1981. 



48 



TREATMENT OF ACID MINE WATER BY WETLANDS 
By Robert L, P. Kleinmann^ 



INTRODUCTION 



Wetlands are a potential natural treat- 
ment system for small flows of acid mine 
water. Previous studies of mine water 
flowing through bogs dominated by Sphag- 
ntjm moss indicate that such a wetland 
removes the iron and reduces acidity, 
without harm to the moss. A group from 
Wright State University studied a site in 
the Powelson Wildlife area in Ohio where 
Sphagnum recurvum was found growing in pH 
2.5 water. Iron, magnesium, sulfate, 
calcixim, and manganese all decreased, 
while pH increased from 2.5 to 4.6 as the 
water flowed through the bog. A natural 
outcrop of limestone located at the down- 
stream end provided sufficient neutrali- 
zation to raise the effluent pH to be- 
tween 6 and 7 (4_) . ^ 

A similar study was conducted by a West 
Virginia University group at Tub Run Bog 
in northern West Virginia (_5 ) . They 
found that acid drainage flowing into the 
wetland area rapidly improved in quality. 
In 20 to 50 m, pH rose from 3.05-3.55 to 
5.45-6.05, while only 10 to 20 m of flow 
through the bog was needed to reduce 
sulfate concentrations from 210-275 mg/L 
to 5-15 mg/L and iron from 26-73 mg/L to 
less than 2 mg/L. Overall, they found 
that the water quality of the bog ef- 
fluent was equal or superior to that 
of nearby streams unaffected by mine 
drainage. 



In laboratory experiments it has been 
shown that 1 kg (wet weight) of S. 
recurvum can remove up to 92 pet of the 
influent 50 mg/L of iron in 16.5 L of pH 
3.8 synthetic mine water solution (3) by 
cation exchange. In a natural wetland, 
bacterial oxidation and sulfate reduction 
in the organic-rich bottom waters add to 
the iron removal capability. It has also 
been demonstrated in the laboratory that 
S. recurvum can tolerate acid mine drain- 
age with iron concentrations as high as 
500 mg/L for 4 weeks. Although the moss 
was stressed, iron removal by cation ex- 
change continued. In the field, higher 
evapotranspiration rates and less ideal 
conditions result in a long-term thresh- 
old of less than 150 mg/L. 

Such field observations and laboratory 
studies suggest that a Sphagnum- dominated 
biological treatment system is feasible. 
Since discharge from such a biological 
treatment system will not meet Federal 
and State pH limitations (pH 6-9) for 
mine water discharges, it was decided to 
incorporate a passive limestone neutrali- 
zation step down-gradient of the moss to 
raise the pH to at least 6.0. Normally, 
limestone in mine water would be rendered 
useless by Fe(0H)3 precipitation, but 
efficient iron removal by the wetland 
would eliminate this problem. 



PILOT-SCALE EVALUATION OF THE BOG-LIMESTONE SYSTEM 



The Bureau of Mines decided that a 
pilot-scale field test was needed to de- 
termine if a bog system could be con- 
structed to treat acid mine water. In 

'Research supervisor, Pittsburgh Re- 
search Center, Bureau of Mines, Pitts- 
burgh, PA. 

^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this paper. 



September 1981, a contract was initiated 
with Peer Consultants and Wright State 
University (subcontractor) to construct a 
pilot-scale test facility at an actual 
mine drainage site. 

A six-section plexiglass tank was con- 
structed and mounted on a steel flat-bed 
trailer. Live Sphagnum moss was harvest- 
ed from the previously studied bog in the 
Powelson Wildlife area and transplanted 



49 



into the plexiglass chamber, which was 
then towed to an acid mine drainage site 
in the Zaleski State Forest in south- 
eastern Ohio. A sketch of the portable 
bog system (fig. 1) shows how water flows 
through the divided chambers sequential- 
ly. The first five sections were packed 
loosely with Sphagnum moss (a mixture of 
S. recurvum v. brevifolium and S. fimbri- 
atum ) , while the last section was packed 
with coarsely crushed limestone. Water 
samples were collected at the intake, at 
the end of the Sphagnum moss, and at the 
outlet. The limestone was also analyzed 
periodically. 

The acid source water for the bog sys- 
tem was an adjacent stream badly contam- 
inated by acid mine drainage. Water was 
already being pumped from the stream by 
the U.S. Geological Survey sampling sta- 
tion at the site. A portion of this 
pumped water was used for our project. 
Flow rates through the bog during the 
initial 8 weeks of the test (June- July 
1982) ranged from 1.4 to 19.8 gal/h owing 
to problems with the pumping equipment 
and inundation of the bog by heavy rain- 
fall. This was subsequently stabilized 
by increasing the diameter of the inlet 
tube and inclining the inlet side of the 
trailer 1.8 in above the outlet side, 
simulating the natural gradient observed 
at the bog in the Powelson Wildlife area. 
A flow rate of approximately 2 gal/h was 
used during August and September 1982; 
after September, flow was Increased to 
approximately 18 gal/h, and then to about 
25 gal/h during 1983. 

Although at times under stress due to 
inundation, the Sphagnum moss remained 



Inlet 



Outlet 



-3.66 m (12')- 



^ 



Sphagnum moss 



i?)- 



Sphagnum moss 



==) 



<= 



Sphagnum moss 



S-^: 



1.93 m 
(6' 4") 



FIGURE 1. - Flow path of acid mine water 
through the bog-limestone system. 

viable throughout the test. Iron was re- 
moved from the acid water by the moss so 
that only minor amounts of visible ferric 
hydroxide coating occurred on the lime- 
stone. Chemical analysis (table 1) con- 
firmed that some coating occurred, but 
the effect on neutralization was insig- 
nificant. Aluminum concentrations, which 
are not significantly affected by the 
Sphagnum moss, may prove to be a problem 
if it turns out that aluminum hydroxide 
floe armors the limestone. 

Dissolved oxygen concentrations indi- 
cate that anaerobic conditions did not 
occur, even at the bottom of the moss 
mat. Sulfate concentrations were not af- 
fected by flow through the bog system, 
and tests for hydrogen sulfide confirm 
that little if any sulfate reduction was 
occurring, presumably owing to the rela- 
tively shallow depth (6 in) of the porta- 
ble bog. Sulfate reduction is an im- 
portant aspect of acid drainage treatment 



TABLE 1 



Results of analysis of limestone samples 



Length of 


Concentration, mg/L 


exposure to 
AMD, weeks 


Iron 


Manganese 


Aluminum 


Calcium 


Magnesium 


Unexposed 

1 


1,200 
1,244 
1,520 
1,538 
1,560 
1,751 
1,784 
1,824 


87.8 
76.0 
79.7 
83.2 

103 

116 

120 

128 


1,080 
722 
643 
1,050 
1,533 
1,739 
1,526 
4,055 


194,000 
204,000 
207,000 
189,700 
200,630 
202,130 
204,100 
201,113 


98,500 
129.000 


3 

5 


128,000 
142,650 


13 

16 

19 


108,770 
104,950 
103,248 


23 


101,128 



50 



by a natural bog (_5) ; its general absence 
in our pilot-scale test implies that 
our iron removal rates are probably 
conservative. 

Figure 2 shows the effect of the Sphag- 
num moss on ferrous iron concentrations 
after the flooding problem was corrected. 
Ferrous iron oxidation averaged 61 pet 
and peaked at 97 pet. Total iron con- 
centrations, which include suspended 
Fe(0H)3 floe, were very erratic, with 
influent concentrations ranging from 15.9 
to 640 mg/L within a week's time. These 
fluctuations reflect resuspension of 
Fe(0H)3 floe from the stream bottom dur- 
ing storms; our small bog did not have 
the detention time to filter out this 
floe well, although presumably a larger 
bog would. The Sphagnum bed typical- 
ly removed 50 to 70 pet of the total 
iron. 



70 



KEY 
Inlet 



^ ^ End of Sphagnum 

o o Outlet 




November December 



FIGURE 2.- Effect of the Sphagnum moss and lime- 
stone on Fe 2+ concentrations in acid mine water. 



700 



600 



500 



£ 



to 

< 

>- 
Q 



o 400 

o 

o 

o 



300- 



200- 



100- 







1 1 11 1 1 
KEY r\ 




• • iniei / \ 

o— o Outlet / \ 




Bog flooded* / V * \ 


— 


'A 


n 


/ 

/ Flow rate y \ \ 


~~ 


1 


V 


j p^s increased — ^ 

II i< 


Inlet line \ W 
clogged \ \* /'^ 

1 II 





July August September October November December 

FIGURE 3. - Effect of the bog-limestone system on the titratable acidity of acid mine water. 



June 
14-30 



51 



Acidity was not significantly affected 
by flow through the Sphagnum mat , but de- 
creased 43 to 90 pet as the water passed 
through the coarsely crushed limestone 
(fig. 3). The 90-pct reduction in acid- 
ity was observed when the initial acidity 
of the influent water exceeded 605 mg/L 
(as CaC03); the 43-pct reduction was ob- 
served when acidity at the inlet was less 
than 150 mg/L. 

Generally, pH increased as acidity de- 
creased. Adsorption of the H"^ ion, al- 
though known to be significant in a 
natural bog (3), did not occur enough in 
our small system to raise the pH as it 
flowed through the Sphagnum moss. How- 
ever, as the water flowed through the 
limestone bed, pH increased an average of 
1.4 and as much as 2.5 units. 



A reduction of 88 pet in the ferrous 
iron concentration in the water was 
achieved in the moss bed. Initially it 
was observed that virtually all of the 
Fe^"*" reduction occurred as the water 
passed through the first two chambers 
containing 24 linear feet (16.5 ft^) of 
the moss. During the final month of 
sampling, after the monitoring sites in 
the portable bog had been changed, this 
reduction in Fe^"*" was found to actually 
occur after the water has passed through 
only one chamber of 12 linear feet (8.3 
ft-') of moss. For the entire bog system, 
at an average flow of 22 gal/h, levels of 
Fe^"*" were reduced by 15 mg/L on average 
at a rate of 5.5 mg/(L»h) or 1.8 mg/L 
per cubic foot of moss. The removal rate 
in the first, chamber was of course much 
higher. 



FULL-SCALE FIELD EVALUATION OF TREATMENT BY WETLANDS 



The Bureau of Mines is now involved in 
field evaluation of the wetland approach 
at mine sites in Pennsylvania and West 
Virginia. The wetlands have been con- 
structed by the respective mining com- 
panies for water treatment; the Bureau is 
facilitating monitoring and evaluation of 
the sites so that others can learn from 
these efforts. Four wetland areas con- 
structed during 1984 and two volunteer 
wetland areas on mined lands are current- 
ly being monitored; two additional sites 
are planned for 1985. 

At the volunteer wetland areas, C&K 
Coal Co. is attempting to enhance already 
established Typha bogs and to divert ad- 
ditional mine water to the wetland areas 
for treatment. At the better studied of 
the two areas, flows range from 30 to 40 
gal/min, with an influent pH of 5.5 to 
5.8. Influent iron concentration aver- 
ages 20 to 25 mg/L; manganese ranges from 
30 to 40 mg/L. The velocity of the water 
in the wetland ranges from 0.1 to 1.0 
ft/s (as measured in less vegetated ar- 
eas) over a 150-ft width with a total 
length of about 85 ft. Effluent water 
has less than 1 rag/L of iron, less than 2 
mg/L manganese, and a near-neutral pH, 
Manganese removal is attributed to bac- 
terial activity (1-2). 



With an understanding of wetlands 
gained from the pilot-scale test and ob- 
servation of the volunteer wetland areas, 
wetland treatment systems have been con- 
structed of Sphagnum alone, and of Sphag- 
num and Typha together. The vegetation 
was transplanted from nearby wetlands by 
personnel of Brehm Laboratory of Wright 
State University and by Ben Pesavento, of 
Environment Analytic, who are also re- 
sponsible for monthly monitoring and sam- 
ple collection. These initial wetland 
areas range in size from 750 to 8,500 
ft^, of which 40 to 60 pet is actual wet- 
ted area, and treat flows of 2-8 gal/min. 
Preliminary results are shown in table 2 
for the three wetland areas constructed 
at least 2 months ago. In addition to 
cation exchange, oxidation, and removal 
as iron sulfides , these results may par- 
tially reflect dilution of iron and man- 
ganese in the bog by ground water. 

It appears that wetlands can be con- 
structed in acid mine water discharges 
and that they will improve drainage 
quality. They require continuous flow, 
without a lot of variation; long-terra 
maintenance requirements have yet to be 
determined. They appear to be most ap- 
propriate for relatively small flows 
(less than 10 gal/min) owing to the large 



52 



TABLE 2. - Performance of wetlands 2 months after construction 
or augmentation, milligrams per liter 



Mine site 


Iron 


Manganese 




Influent 


Effluent 


Influent 


Effluent 


Mine 1................. 


24 

8.7 
24 


0.5 

1.2 

.6 


43.8 
24.5 
16 


16.1 


Mine 2 


15.5 


Mine 3 


3.8 



surface area requirement — we like to al- 
low 200 ft^ of wetted area per gallon per 
minute of flow. However, only space lim- 
its the extension of this system to 
greater flows. An attempt will be made 



to treat acid flows of 50 to 100 gal/min 
in larger wetland systems, starting with 
partial treatment in 1985 and, if suc- 
cessful, followed by full-scale tests in 
1986. 



REFERENCES 



1. Emerson, S, , S. Kalhorn, L. Jacobs, 
B. M Tebo, K. H. Nealson, and R. A. Ros- 
son. Environmental Oxidation Rate of 
Manganese (II): Bacterial Catalysis. 
Geochim. et Cosmochim. Acta, v. 46, 1982, 
pp. 1073-1079. 

2. Gregory, E., and J. T. Staley. 
Widespread Distribution of Ability To 
Oxidize Manganese Among Freshwater Bac- 
teria. App. and Environ. Microbiol. , v. 
44, No. 2, 1982, pp. 509-511. 

3. Harris, R. L. , T. 0. Tiernan, 
J. Hinders, J. G. Solch, B. E. Huntsman, 
and M. L. Taylor. Treatment of Mine 
Drainage From Abandoned Mines by Biologi- 
cal Iron Oxidation and Limestone Neutral- 
ization. Peer Consultants report pre- 
pared for Bureau of Mines under contract 



J0113033, 1984, 113 pp.; available from 
Robert Kleinmann, BuMines , Pittsburgh, 
PA. 

4. Huntsman, B. E., J. G. Solch, and 
M. D. Porter. Utilization of Sphagnum 
Species Dominated Bog for Coal Acid Mine 
Drainage Abatement. Geol. Soc. America 
(91st Ann, Meeting) Abstracts, Toronto, 
Ontario, Canada, 1978, pp. 322. 

5. Wieder, R. K. , G. E, Lang, and 
A. E. Whitehouse. Modification of Acid 
Mine Drainage in a Fresh Water Wetland. 
Paper in Proceedings , Acid Mine Drainage 
Research and Development , 3d WV Surface 
Mine Drainage Task Force Sjmiposium, WV 
Surface Mine Drainage Task Force, 
Charleston, WV, 1982, pp. 38-62. 



53 



IN-LINE AERATION AND TREATMENT OF ACID MINE DRAINAGE: PERFORMANCE 
AND PRELIMINARY DESIGN CRITERIA 

Bv Terry Ackman^ and Robert L. P. Kleinniann^ 



INTRODUCTION 



It is estimated that the U.S. coal 
mining industry spends over $1 million 
per day treating acidic mine water so 
that it can be legally discharged ( 4_) . ^ 
This figure includes the amortized cost 
of the large water treatment plants (a 
conventional lime neutralization facility 
typically costs over $1 million to 
construct), treatment chemicals (lime, 
soda ash, sodium hydroxide, flocculant, 
etc.), maintenance, electric power, and 
labor. 

Although expensive, conventional acid 
mine drainage (AMD) treatment is a simple 
process. The water is neutralized, typi- 
cally to a pH of 8 to 9, and then aerated 
to oxidize the iron to the Fe-^"*" state, 
causing precipitation of Fe(0H)3 (Yellow- 
boy) sludge. The water is then separated 
from the sludge in a series of settling 
basins or ponds and discharged. 

Above a pH of 3.5, the rate of iron ox- 
idation is controlled by dissolved oxygen 
(DO) and pH. Fully aerated mine water 
contains about 8 mg/L DO, which is con- 
sumed at the rate of 1 mg/L for every 7 
mg/L Fe"*"^ oxidized; consequently, the 
DO initially present can only oxidize 
50 to 60 mg/L Fe^"^ ^]J • ^^ °^^ assumes, 
though, that DO is not depleted but in- 
stead is maintained at a constant level 
by continuous aeration, the effect of pH 
on the rate of iron oxidation can be 
calculated. Table 1 illustrates the 
effect of pH on the required aeration 
time for an initial Fe^"*" concentration of 
100 mg/L. Inspection of the reaction 
times listed in table 1 reveals why pH is 

Mining engineer. 

^Research supervisor. 

^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this paper. 



raised to 7,5 or above at most treatment 
plants to quickly oxidize the ferrous 
iron, 

TABLE 1. - Time required to oxidize 97 
pet of 100 mg/L Fe^"*" at various con- 
stant pH's, and constant oxygen sat- 
uration (8 mg/L DO) 



pH 



Time, h 



4,5 3.5 

5 3.5 

5.5 3.5 

6 3.5 

6.5 3.5 

7 3,5 

7.5 3,5 

8 3,5 

8,5 3,5 



10^ 
10^ 

102 

IQl 

10-' 
10-2 
10-3 
10-^ 



For replenishment of DO in mine water, 
settling ponds or lagoons are constructed 
wide and shallow to maximize diffusion of 
oxygen into the water and thereby in- 
crease oxygen transfer from the atmos- 
phere. However, oxygen diffusion is rel- 
atively slow (9^) , so that at many sites 
supplementary aeration sources are neces- 
sary (8^), For example, oxygen transfer 
can be increased by increasing turbu- 
lence. This is typically accomplished by 
incorporating a series of open-channel 
drops in the flow path of the water. 
Mechanical aerators can also be used to 
continuously introduce bubbles of air in- 
to the water. This continuous replenish- 
ment of DO is effective in maintaining a 
rapid reaction rate, but it also has dis- 
advantages: a separate aeration tank or 
basin is required; there are high initial 
capital costs; and there are operating 
costs associated with power consumption 
and maintenance, especially where gypsum 
precipitation is a problem. 



54 



This report describes a Bureau of 
Mines-designed treatment system that has 
been tested at mine sites in Pennsylvania 
and West Virginia. The in-line aeration 
and treatment system (ILS) functions in 
existing AMD pipelines, using energy pro- 
vided by existing mine water discharge 



pumps. It appears to be a low-cost al- 
ternative to conventional treatment 
plants and, in fact, appears to accel- 
erate iron oxidation rates. The system 
has no moving parts and thus has the ad- 
vantages of low maintenance and operating 
costs. 



UNIT DESCRIPTION 



The ILS consists of two off-the-shelf 
components: a jet pump O) and a static 
mixer. Both components can be described 
as aeration and mixing devices. Jet 
pvimps are simply nozzles that entrain air 
by Venturi action (fig. 1). The jet pump 
used is made of polyvinyl chloride (PVC). 
Water enters under pressure and is con- 
verted by the jet pump into a high- 
velocity stream. This stream then passes 
through a suction chamber, which is open 
to the atmosphere. If the system is be- 
ing used for neutralization as well as 



aeration, the suction chamber also serves 
as the injection point for the neutraliz- 
ing material. Multiple jet pump units 
may be placed in parallel as long as wa- 
ter pressures of at least 20 psi are 
maintained. 

After passing through the jet pump, the 
flow enters the static mixer (fig. 2). 
The static mixer consists of 1-ft sec- 
tions of pipe made of copolymer poly- 
propylene resins, laminated together end 
to end with fiberglass. Inside each 



Suction chamber 



Nozzle 




Parallel section 



\ \ V \ \ \ \ X \ v ^ \ \^ 



T 



\\\\\s \\xs 



Diffuser 




Suction 



FIGURE 1. - Jet pump diagra 



m. 



Static mixer 



Flow 




•. • • . 



FIGURE 2. - Diagram of the static mixer. Air bubbles are reduced in size by the turbulence, 
significantly increasing interfacial contact. 



55 



section is a 1-ft helix that forces the 
water to follow a spiral path. Static 
mixers are used routinely in sewage and 
industrial waste water treatment plants 
as vertical airlift aeration and mixing 
units, but that design was modified some- 
what for this horizontal application: 



each helical unit was rotationally offset 
90° from its neighbor, thereby interrupt- 
ing the corkscrew every foot and enhanc- 
ing the mixing action. Eight 1-ft sec- 
tions were used, which provided the 
contact time of a normal 32-ft pipe be- 
cause of the induced spiral flow. 



PERFORMANCE CHARACTERISTICS 



AERATION OF NEAR-NEUTRAL MINE WATERS 

The ILS was first tested as an aeration 
unit at a mine site in Greene County, PA. 
Influent Fe^"^ levels were erratic but 
often exceeded 100 mg/L at near-neutral 
pH. As an alternative to mechanical 
aeration, the ILS was installed at the 
end of the discharge pipe from the under- 
ground mine. 

Monitoring the discharge from the site 
began on the fourth day after installa- 
tion of the ILS. Ferrous iron concentra- 
tions dropped from 10 to 20 mg/L before 
installation of the ILS to 0.2 to 0.9 
mg/L. Total iron concentrations fell 
from over 20 mg/L to less than 2 mg/L. 



conducted at actual mine sites using 
sodium hydroxide (NaOH) , quick lime 
(CaO), or hydrated lime (Ca(0H)2), with 
the latter two added as slurries. The 
effluent pH was easily adjusted in each 
case, and the violent mixing action of 
the ILS minimized excessive lime use. 

Tables 2-4 allow the comparison of ac- 
tual NaOH or lime consvimption with theo- 
retical "best case" neutralization. The 
theoretical values are derived assuming 
optimal efficiency (90 pet for CaO, 95 
pet for Ca(0H)2, and 99 pet for NaOH) and 
a pH endpoint of 8.3 ( 5^) ; our experience 
indicates that conventional treatment 
plants use 25 pet more lime than these 
calculated values. 



Subsequent aeration tests were conduct- 
ed with more acidic water. Iron oxida- 
tion continued to be impressive despite 
an influent pH of 4.6 to 5.6. Figure 3 
is a graph of average Fe^"*" values for all 
samples of pH 5.5 ±0.2. Although very 
little iron oxidation occurred in the 
ILS, the discharge from the first pond 
(24-h detention time) averaged only 6 
mg/L Fe^"*". This represents not only much 
greater iron oxidation than without the 
ILS at this pH, but also a much faster 
rate than expected in oxygen-saturated 
water (table 1). A more detailed analy- 
sis of this topic may be found in RI 8868 
(2). 

SIMULTANEOUS NEUTRALIZATION 
AND AERATION 

The suction port of the jet pumps can 
be used for addition of neutralizing 
chemicals without significantly interfer- 
ing with air intake. Field tests were 



150 r 



d) 100 

E 

z 

O 

tr 



CO 

Z) 

O 
tr 

LU 

LL 



50 




IW^ 



RAW 
WATER 



AFTER 
POND 



FIGURE 3. - Effect of the ILS as an aeration sys- 
tem on average Fe 2' concentration at pH 5,5 :t0.2 at 
the Greene County, PA, site. Pond has a 24-h de- 
tention time. 



56 



TABLE 2. - NaOH use at site 2--Braxton County, WV 



Test 


Raw 


Net acidity 


Flow, 


Na in 


Na in 


Treated 


Theoretical 


Actual 


run 


pH 


of raw 


gal/mln 


raw water. 


treated 


pH 


NaOH use. 


NaOH use, 






water, mg/L 




lag/L 


water, mg/L 




Ib/min 


Ib/min 



SINGLE TREATMENT 



1... 


3.2 


3,784 


521 


22 


1,243 


5.1 


13.4 


5.3 


2... 


3.3 


3,951 


469 


22 


1,216 


5.3 


12.6 


4.7 


3... 


3.2 


3,784 


543 


23 


1,000 


5.2 


14.0 


4.4 


4... 


3.2 


4,022 


533 


23 


1,176 


5.0 


14.6 


5.1 


5... 


2.7 


3,689 


385 


27 


1,634 


6.6 


9.7 


5.2 


6... 


2.6 


3,689 


533 


23 


1,094 


4.9 


13.4 


4.8 


7... 


2.5 


3,713 


530 


23 


1,209 


4.9 


12.9 


5.2 


8... 


2.8 


3,677 


261 


35 


1,779 


6.8 


6.5 


3.8 


9... 


2.9 


3,641 


345 


35 


3,558 


12.8 


8.5 


10.1 




DOUBLE TREATMENT 


10.. 


4.8 


75 


543 


1,860 


1,865 


8.4 


0.3 


0.03 


11.. 


4.6 


89 


475 


1,831 


2,193 


11.3 


.3 


1.4 


12.. 


4.6 


87 


340 


1,865 


2,021 


9.9 


.2 


.4 


13.. 


4.6 


95 


523 


1,728 


2,175 


10.7 


.4 


1.9 


14.. 


4.6 


71 


475 


1,514 


2,153 


10.6 


.2 


2.5 


15.. 


4.3 


68 


337 


1,888 


1,872 


8.6 


.1 


.04 



TABLE 3. - Lime use at site 3 Armstrong Country, PA 



Sam- 


Raw 


Net acidity 


Flow, 


Ca in 


Ca in 


Treated 


Theoretical 


Actual 


ple 


pH 


of raw 


gal/min 


raw water. 


treated 


pH 


lime use. 


lime use. 






water, mg/L 




mg/L 


water, mg/L 




Ib/min 


Ib/min 


1... 


2.7 


830 


363 


284 


1,078 


11.7 


1.7 


4.4 


2... 


3.0 


753 


363 


271 


268 


3.1 


1.5 


.0 


3... 


3.0 


830 


363 


277 


618 


7.3 


1.7 


1.9 


4... 


3.0 


791 


363 


279 


671 


8.8 


1.6 


2.2 


5... 


2.9 


830 


363 


287 


608 


5.7 


1.7 


1.8 


6... 


N/A 


791 


363 


280 


692 


8.8 


1.6 


2.3 


7... 


2.9 


830 


363 


286 


617 


6.9 


1.7 


1.8 



TABLE 4. - Lime use at site 4 Westmoreland County, PA 



Sam- 
ple 



Raw 
pH 



Net acidity 

of raw 
water, mg/L 



Flow, 
gal/min 



Ca in 

raw water, 

mg/L 



Ca in 

treated 

water, mg/L 



Treated 
pH 



Theoretical 

lime use, 

Ib/min 



Actual 

lime use, 

Ib/min 



1 

2 

3 

4 

5 

6 

7 

8l 

9 

Plant^ 



5.6 
5.7 
5.4 
5.4 
5.6 
5.5 
5.5 
5.4 
5.4 

4.8 



973 

877 
1,010 
1,040 

942 
1,012 
1,062 

986 
1,018 

1,280 



469 
457 
457 
469 
542 
485 
485 
485 
485 

1,450 



445 
454 
424 
419 
451 
425 
421 
420 
405 

421 



1,015 
1,020 
1,057 
1,164 

749.8 

901 

909 
1,018 

948 

1,081 



8.4 
7.7 
7.0 
6.9 
6.6 
7.0 
6.9 
7.1 
7.0 

8.2 



2.6 
2.3 
2.6 
2.8 
2.9 
2.8 
2.9 
2.7 
2.8 

10.5 



4.1 
4.0 
4.5 
5.4 
2.5 
3.5 
3.3 
4.5 
4.1 

^14. 7 
419.1 



^Fe and Mn in filtered samples were within effluent standards, 
^Normal plant operation. 
^Measured by chemical analysis. 
'^Physically measured dry feed. 



57 



Table 2 represents a two-stage process, 
usig NaOH to treat mine water with high 
acidity and high iron. Samples 1 through 
9 represent a single treatment pass 
through the ILS from pond 1 to pond 2 
(initially empty before the test). Sam- 
ples 10 through 15 represent water pumped 
from pond 2 through the ILS to pond 3 36 
h after the first treatment. Effluent 
water from the two-stage treatment met 
effluent standards. Actual NaOH usage 
was calculated from the difference in 
sodium concentrations in unfiltered, 
acidified samples of treated and raw 
water. Theoretical NaOH requirement was 
calculated by Lovell's equations (_5 ) . 
NaOH use was approximately half of that 
theoretically required. However, iron 
was precipitated as both Fe(0H)3 and 
Fe(0H)2 in the first step of the treat- 
ment. As explained later, Fe(0H)2 will 
eventually oxidize, adding acidity to the 
pond water. 

Table 3 summarizes the results of a 
field test using Ca(0H)2. This operation 
did not allow a quantitative comparison 
with actual consumption of lime by the 
conventional water treatment plant, but 
the plant operator felt that lime usage 
was reduced enough to design an ILS to 
replace the existing system. Except at 
high pH (sample 1), the ILS values met 
discharge criteria and approached the 
theoretical optimal values for lime con- 
sumption. As discussed later, both iron 
and manganese were reduced to effluent 
levels at a discharge pH as low as 6.9, 
indicating that greater potential cost 
savings can be obtained. 

Table 4 presents the results of a field 
test using CaO slurry to neutralize water 
being pumped from an underground mine 
pool. Owing to the high levels of dis- 
solved iron (over 500 mg/L) , the ILS unit 
could not oxidize all of the iron in a 
single pass; as at the NaOH site (table 
2) , some of the iron precipitated as 
Fe(0H)2. Water sample 8, which met dis- 
charge standards after filtration, can be 
used for comparing actual costs with 
those for operation of the conventional 
treatment plant (table 4, bottom row). 
Since flow through the ILS is one-third 



that of normal plant operation, the ob- 
served lime use of 4.5 Ib/min at pH 7.1 
must be scaled up to 13.5 Ib/min. This 
is within 1 pet of the amount of lime 
consumed in neutralizing acidity during 
operation of the conventional treatment 
plant (as calculated from chemical analy- 
sis) but is 30 pet more efficient than 
actual lime use, as measured during nor- 
mal plant operation. Analysis of the 
sludge during operation of the conven- 
tional treatment plant confirms that a 
lot of unreacted lime is being wasted, 
especially in the aeration basin, owing 
to insufficient mixing action, 

IRON OXIDATION 

During field testing of the ILS, it be- 
came apparent that iron oxidation was 
proceeding much faster thdn anticipated. 
At low pH (4.6 to 5.5), iron oxidation 
was accelerated by a factor of 10 to 400; 
at near-neutral pH (6.9 to 7.5), iron ox- 
idation was accelerated by as much as 
1,000 (2^). Figure 3 illustrates iron ox- 
idation at the Greene County, PA, test 
site; 98.7 pet of the 190 mg/L Fe^"^ in 
the influent water was oxidized in the 
4-8 transit time in the ILS. Most of 
this oxidation apparently occurred in the 
jet pump section of the ILS since water 
samples collected between the jet pump 
and the static mixer had an average pH of 
6.7 and an Fe^"*" concentration of only 4.8 
mg/L. To obtain such rapid iron oxida- 
tion in a conventional water treatment 
system, the pH would have to be raised to 
at least 8.5. 

However, the iron oxidation capacity of 
the existing ILS design is limited. As 
influent Fe^"*" concentrations approach 300 
mg/L, the efficiency of the system de- 
creases. Tables 5 and 6 document field 
trials with average influent Fe^"*" concen- 
trations of 965 and 527 mg/L, respective- 
ly. The amount of Fe^''" oxidized during 
transit through the ILS ranged between 
283 and 479 mg/L using NaOH (table 5) and 
between 163 and 345 rag/L using CaO (table 
6). The amount of Fe^"*" oxidized was cal- 
culated as the difference between Fe^"*" 
concentrations in acidified, unfiltered 
samples of raw and treated water. The 



58 











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59 



amount of Fe^"'" removed was calculated in 
the same way from unacidified, filtered 
treated water. Filtering was assumed to 
approximate settling of iron hydroxides. 

At these high levels of influent Fe^"*", 
additional quantities of Fe^"*" were re- 
moved as Fe(0H)2, which produces a green 
sludge in the ILS effluent at a pH as low 
as 4.9. Fe(0H)2 is unstable below a pH 
of about 7; its formation in the ILS sug- 
gests that a transient pH of at least 8 
(6) exists at the point of alkaline in- 
jection and that the dissolution of oxy- 
gen cannot match the chemical oxygen de- 
mand represented by the Fe^"*" at that pH. 
The formation of Fe(0H)2 has both advan- 
tages and disadvantages: the precipita- 
tion of both sludge forms reduces dis- 
solved iron concentrations , allowing 
discharge of the effluent water, but the 
Fe(0H)2 sludge will gradually oxidize to 
Fe(0H)3, lowering the pH of the sludge 
and, through diffusion, the effluent wa- 
ter. The difference on tables 5-7 be- 
tween iron oxidized and iron removed re- 
flects formation and precipitation of 
Fe(0H)2. 

The apparent high transient pH in the 
jet pump may partially explain the ex- 
tremely high rate of iron oxidation in 
the ILS. Table 1 indicates that a 1-s pH 
of 8.5 to 9.0 would be sufficient if DO 
is continuously replenished; an instan- 
taneous pH over 10 would reduce the 



required reaction time to milliseconds in 
whatever fraction of the fluid is at a 
high pH. It is not known whether the 
apparent limitation on iron oxidation is 
due to limited air intake and the rate of 
oxygen dissolution (from the bubbles into 
the water) , or to limited catalysis by 
some other mechanism. 

Apparent oxidation of dissolved iron in 
the pond, after ILS treatment, continues 
to be rapid for several days (J^) . This 
apparent effect is caused by fine-ground 
suspended Fe(0H)2 or Fe(0H)3 particles 
that are analyzed as dissolved iron 
in unfiltered samples. These particles 
slowly settle in the pond, mimicking oxi- 
dation and hydrolysis; filtration with a 
0.45 ym filter confirms this explanation. 

REMOVAL OF MANGANESE 

Manganese, when present in mine water 
at concentrations greater than 4 mg/L, 
can significantly add to the costs of wa- 
ter treatment. In a conventional treat- 
ment plant, the pH must be raised to 
above 10 (typically 10.5) for rapid oxi- 
dation and removal of manganese; this 
adds greatly to the costs of neutraliza- 
tion, produces an effluent that is unac- 
ceptably alkaline, and can cause redisso- 
lution of iron. Three of the four field 
sites where the ILS was tested had manga- 
nese problems. Manganese averaged 68 mg/ 
L at the West Virginia site (table 5), 



TABLE 7. - Oxidation site 3 — Armstrong County, PA 



Run 1 



Run 2 



Run 3 



Run 4 



Run 5 



Run 6 



Run 7 



Fe^"^ oxidized^ mg/L. . 

Fe^"^ oxidized pet. . 

Fe^* removed-^ mg/L. . 



Fe 



2 + 



removed pet . . 



lin. removed (unfiltered) rag/L.. 

Mn removed (unfiltered) pet.. 

Mn removed (filtered) mg/L.. 

Mn removed (filtered) pet.. 

O2 consumed std ft-^/min,. 

O2 consumed Ib/min. . 

Effluent pH 

Initial Fe^"^ concentration. .. .mg/L. . 



6 

7 

0.3 

0.4 

0.2 

2 

-0.2 

2 

0.02 

0.002 

3.1 

80.5 



75 

98 

75 

99 

2.1 

21 

9 

95 

0.4 

0.03 

11.7 

75.9 



67 

94 

70 

99 

0.1 

1 

9 

91 

0.3 

0.02 

7.3 

71.3 



74 

98 

74 

99 

0.4 

4 

9 

90 

0.3 

0.03 

8.8 

74.7 



77 

97 

78 

98 

-0.3 

-3 

2 

24 

0.4 

0.03 

5.7 

79.5 



76 

99 

77 

99 

-0.6 

-7 

9 

99 

0.4 

0.03 

8.8 

77.3 



78 

99 

78 

99 

-0.4 

-4 

6 

69 

0.4 

0.03 

6.9 

79.5 



Untreated sample, run through ILS without neutralization. 
^Fe^* oxidized as Fe(0H)3. 
^Fe^* removed as Fe(0H)3 and Fe(0H)2. 



60 



14 mg/L at the Westmoreland County, PA, 
site (table 6), and about 10 mg/L at the 
Armstrong County, PA, site (table 7). At 
all three sites, manganese was reduced to 
within effluent limits after passage 
through the ILS. 

At the West Virginia site, the first 
treatment step raised the pH to 4.9 to 
6.8 and had little apparent effect on 
manganese concentrations in unfiltered 
samples. However, 6 h after discharge to 
the pond, and despite the low pH, man- 
ganese concentrations had fallen to 13.5 
mg/L, an 80-pct reduction. Sealed water 
samples kept in the laboratory showed 
similar declines in manganese concentra- 
tions, with no detectable dissolved 
manganese present after 11 days of 
storage. 

At the Westmoreland County site, water 
treated to a pH of 7.1 or greater met 
effluent standards for manganese after 
filtration. Filtered samples that had 
been treated to a pH of 6.9 to 7.0 ap- 
proached manganese effluent standards 



(3.1-5.6); it was not possible to collect 
samples after settling. 

At the Armstrong County site, a similar 
pattern was observed. Fe^"*" was reduced 
to below effluent standards at a pH of 
5.7 and up, but manganese exceeded ef- 
fluent limits under pH 7.3. ILS test 
runs at pH 7.3 or above met effluent 
standards. 

It appears that manganese was precipi- 
tating as very small particles during 
neutralization and aeration in the ILS. 
Filtration removed most of these parti- 
cles; settling removed all of them. It 
is possible that the transient pH in the 
jet pump was high enough to allow for 
rapid formation of Mn02. Alternatively, 
it is possible that the manganese is be- 
ing removed from solution as a coprecipi- 
tate on particles of iron hydroxide as 
they form and swirl in the ILS. It has 
previously been shown that adsorption of 
manganese by Fe(0H)3 increases rapidly 
above pH 8, rising from 0.15 to over 0.6 
mol Mn2+ per mol Fe^+ at pH 8.6 (7). 



PRELIMINARY DESIGN SPECIFICATIONS 



Three parameters should be considered 
in the design of the ILS: available wa- 
ter pressure, flow, and influent Fe^"*" 
concentration. Table 8 partially sum- 
marizes flow capacity of the existing ILS 
design at various water pressures. In 
general, adding jet pumps (in parallel) 
increases capacity. The ILS that was 
designed and tested by the Bureau had 
valves on two of the three jet pumps. 
This allowed for variable flow rates and 
is a potentially useful feature on sites 
where surface runoff during storm events 
determines treatment requirements. 

Additional helixors influence flow ca- 
pacity and may increase oxygen transfer. 

TABLE 8. - Flow rates for 



Increased water pressure increases flow 
capacity. If flows are above 500 gal/ 
min, larger capacity jet pumps can be 
substituted or additional jet pumps can 
be placed in parallel. 

If Fe^"*" levels are above 300 mg/L, a 
two-stage treatment process may be neces- 
sary. This can actually be quite effi- 
cient, as shown in tables 2 and 5, and 
does not necessarily require a second ILS 
unit. For example, a surface mine can, 
by installing valves in multiple suction 
and discharge lines , pump the once- 
treated water from the first-stage set- 
tling pond through the same ILS to 
another settling pond. Similarly, an 

the ILS, gallons per minute 



Test design 


20 psi 


30 psi 


40 psi 


50 psi 


64 psi 


3 jet pumps in parallel with 1 helixor. . 
3 jet pumps in parallel with 2 helixors 
in series .,, 


NA 

329 

NA 


411 
317 
261 


469 
457 
310 


521 
542 
344 


NA 
NA 


2 jet pumps in parallel with 2 helixors 
in series 


363 



NA Not available. 



61 



underground mine that is intermittently 
discharging through an ILS unit into a 
settling pond can pump from the pond 
through the same ILS to a second settling 
pond while the underground pump is off. 
However, if there is continuous flow, 
then two ILS units and a second pump are 
necessary. Our tests of the two-step 
process indicate that a 50-pct reduction 
in neutralization costs is possible with 
such a system (table 2). 

Actual oxygen consumption rates, as 
calculated from the amount of iron oxi- 
dized during passage through the ILS, are 
shown on tables 5-7. Air transfer tables 
provided by the jet pump manufacturer do 
not appear to correlate with observed 
oxygen consumption. For example, in our 
ILS design, sample 2 (table 5) consumed 
2.3 std ft^/min O2 operating at 40 psi, 
with three jet pumps in parallel and with 
10 psi back, pressure; the manufacturer's 
tables predict 1.5 std ft-^/min per jet or 
4.5 std ft^/min of air intake for the 
three-jet pump system. Sample 1, operat- 
ing at 50 psi, consumed 2.4 std ft-^/min 
O2; the same tables predict std ft^/ 
mln of air intake under these operating 
conditions. Actual air flow measure- 
ments are needed so that oxygen transfer 
can be quantified. 



Another aspect of system design is 
cost. The 3-in PVC jet pumps and static 
mixers cost about $900 and $2,500 each, 
respectively. Associated PVC plumbing 
costs about $500. For our tests we pur- 
chased a hydraulic pump with a diesel 
power unit capable of providing pressures 
up to 50 psi with three jet pumps, but 
any heavy-duty pump should serve. The 
total cost is, of course, much less than 
for construction of a conventional em- 
placed treatment system. Operating costs 
should also be low owing to the efficient 
mixing action, efficient iron oxidation, 
and lack of moving parts. 

There are other advantages. The system 
is small, and if desired, portable. It 
requires no electrical power, although it 
does add slightly to the Ipad on the mine 
water discharge pump (approximately 10 
pet). The basic design is simple and 
easily modified to cover a wide range of 
flow and pressure conditions and can 
operate continuously or intermittently. 
It can also be dismantled easily for use 
elsewhere if water treatment is no long- 
er required. Finally, although settling 
ponds are required, they do not serve as 
aeration basins and therefore do not re- 
quire as large an area as would be the 
case for a conventional treatment plant. 



REFERENCES 



1. Ackman, T. E. , and R. L. P. Klein- 
mann. In-Line Aeration and Treatment of 
Acid Mine Drainage. Paper in Proceed- 
ings, 1984 Symposium on Surface Mining, 
Hydrology, Sedimentology , and Reclama- 
tion, Dec. 3-7, 1984, Lexington, KY, ed. 
by D. H. Graves. Univ. KY, Lexington, 
KY, pp. 29-34. 

2. . In-Line Aeration and Treat- 
ment of Acid Mine Drainage, BuMines RI 
8868, 1984, 9 pp. 

3. Gosline, J. E. , and M. P. O'Brien. 
The Water Jet Pump. Univ. CA, Publ. 
Eng., V. 3, No. 3, 1942, pp. 167-190. 

4. Kim, A. G. , B. S. Heisey, R. L. P. 
Kleinmann, and M. Deul . Acid Mine 
Drainage: Control and Abatement Re- 
search. BuMines IC 8905, 1982, 22 pp. 



5. Lovell, H. L, The Reagents. Ch. 3 
in Fundamentals of Water Pollution Con- 
trol in Coal Mining. PA State Univ., 
State College, PA, 1982, 360 pp. 

6. Snoeyink, V, L, , and D, Jenkins, 
Water Chemistry, Wiley, 1980, 463 pp. 

7. Sturam, W. , and J. J. Morgan, 
Aquatic Chemistry, Wiley-Interscience, 
2d ed., 1981, 780 pp, 

8. U.S. Environmental Protection Agen- 
cy. Neutralization of Acid Mine Drain- 
age. EPA-600/2-83-001, 1983, 231 pp. 

9. Weber, W, J, Physiochemical Pro- 
cesses. Wiley-Interscience, 1972, 640 
pp. 



ifU.S. CPO: 1983- 50>fl19 20,018 



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